Block copolymer particles

ABSTRACT

Block copolymer particles, and related compositions and methods, are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims priority under35 U.S.C. § 120 to, U.S. patent application Ser. No. 11/314,056, filedon Dec. 21, 2005 and entitled “Block Copolymer Particles”, and U.S.patent application Ser. No. 11/314,557, filed on Dec. 21, 2005 andentitled “Block Copolymer Particles”, both of which are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

The disclosure relates to block copolymer particles, and to relatedcompositions and methods.

BACKGROUND

Agents, such as therapeutic agents, can be delivered systemically, forexample, by injection through the vascular system or oral ingestion, orthey can be applied directly to a site where treatment is desired. Insome cases, particles are used to deliver a therapeutic agent to atarget site.

SUMMARY

In one aspect, the invention features a particle including a blockcopolymer and having at least one pore. The particle has a diameter ofabout 3,000 microns or less.

In another aspect, the invention features a method of making a particleincluding a block copolymer and having at least one pore. The methodincludes generating a drop including the block copolymer and at leastone salt, water-soluble polymer, base, or combination thereof, andforming the drop into the particle.

In an additional aspect, the invention features a method of making aparticle including a block copolymer and having at least one pore. Themethod includes forming a drop including the block copolymer and asolvent, and removing some or all of the solvent from the drop to formthe particle.

Embodiments can also include one or more of the following.

The particle can include a therapeutic agent, such as one or moreproteins, genes, or cells, DNA, RNA, insulin, or a combination thereof.

The block copolymer can include at least one first block having a glasstransition temperature of at most 37° C. and at least one second blockhaving a glass transition temperature of greater than 37° C. The firstblock can include at least one polyolefin block. In some embodiments,the first block can include at least one isobutylene monomer. The secondblock can include at least one vinyl aromatic block, methacrylate block,or a combination thereof. In certain embodiments, the first block (e.g.,the polyolefin block) can include at least one isobutylene monomer, andthe second block (e.g., the vinyl aromatic block) can include at leastone monomer selected from styrene, α-methylstyrene, and combinationsthereof.

The block copolymer can have the formula X-(AB)_(n), in which A is apolyolefin block, B is a vinyl aromatic block or a methacrylate block, nis a positive whole number, and X is an initiator. In some embodiments,A can have the formula —(CRR′—CH₂)_(n)—, in which R and R′ are linear orbranched aliphatic groups or cyclic aliphatic groups, and B is amethacrylate block or a vinyl aromatic block. In certain embodiments, Bincludes at least one monomer selected from methylmethacrylate,ethylmethacrylate, hydroxyethyl methacrylate, and combinations thereof.

The block copolymer can have the formula BAB or ABA, in which A is afirst block and B is a second block.

The block copolymer can have the formula B(AB)_(n) or A(BA)_(n), inwhich A is a first block, B is a second block, and n is a positive wholenumber.

The block copolymer can include from about 45 mol percent to about 95mol percent of polyolefin blocks. The block copolymer can have amolecular weight of more than about 40,000 Daltons. In some embodiments,the block copolymer can include polyolefin blocks having a combinedmolecular weight of from about 60,000 Daltons to about 200,000 Daltonsand vinyl aromatic blocks having a combined molecular weight of fromabout 20,000 Daltons to about 100,000 Daltons.

The block copolymer can be styrene-isobutylene-styrene. The blockcopolymer can be biocompatible.

The block copolymer can form a coating on the particle.

The particle can include a bioabsorbable material. In some embodiments,the particle can include a hydrogel. In certain embodiments, theparticle can include a second polymer (e.g., that is blended with theblock copolymer). In some embodiments, the second polymer can be a blockcopolymer. In certain embodiments, the second polymer can be selectedfrom polyvinyl alcohols, polyacrylic acids, polymethacrylic acids, polyvinyl sulfonates, carboxymethyl celluloses, hydroxyethyl celluloses,substituted celluloses, polyacrylamides, polyethylene glycols,polyamides, polyureas, polyurethanes, polyesters, polyethers,polystyrenes, polysaccharides, polylactic acids, polyethylenes,polymethylmethacrylates, polycaprolactones, polyglycolic acids,poly(lactic-co-glycolic) acids, and styrene maleic anhydride copolymers.

The particle can have a diameter of about 3,000 microns or less.

The pore can have a maximum dimension of at least 0.01 micron (e.g., atleast about 0.1 micron, at least about 35 microns) and/or at most about300 microns (e.g., at most about 35 microns, at most about 0.1 micron).The particle can have a plurality of pores. Some or all of the pores canhave a maximum dimension of from 0.01 micron to about one micron, and/orsome or all of the pores can have a maximum dimension of from about 10microns to about 300 microns.

Forming the drop into the first particle can include contacting the dropwith a solution including water. The solution can have a temperature ofat least about 20° C. (e.g., at least about 25° C., at least about 30°C., at least about 50° C., at least about 75° C.) and/or at most about100° C. (e.g., at most about 75° C., at most about 50° C., at most about30° C., at most about 25° C.).

The method can include generating the drop including the block copolymerand a salt, and forming the drop into the first particle can includedissolving the salt. The salt can include at least one of sodiumchloride, calcium chloride, and sodium bicarbonate. Generating the dropincluding the block copolymer and a salt can include combining the blockcopolymer with at least one particle including the salt. The particleincluding the salt can have a maximum dimension of at least 0.01 micronand/or at most about 300 microns. In some embodiments, generating thedrop including the block copolymer and a salt can include combining theblock copolymer with a plurality of particles including the salt. Someor all of the particles including the salt can have a maximum dimensionof from 0.01 micron to about one micron, and/or some or all of theparticles including the salt can have a maximum dimension of from about10 microns to about 300 microns.

The method can include generating the drop including the block copolymerand a water-soluble polymer. The water-soluble polymer can include atleast one of polyethylene glycol, polyvinylpyrrolidone,carboxymethylcellulose, and hydroxyethylcellulose.

The method can include generating the drop including the block copolymerand a base. The base can include at least one of sodium bicarbonate,ammonium bicarbonate, and potassium bicarbonate. Generating the dropincluding the block copolymer and a base can include combining the blockcopolymer with at least one particle including the base. The particleincluding the base can have a maximum dimension of at least 0.01 micronand/or at most about 300 microns. In some embodiments, generating thedrop including the block copolymer and a base can include combining theblock copolymer with a plurality of particles including the base. Someor all of the particles including the base can have a maximum dimensionof from 0.01 micron to about one micron, and/or some or all of theparticles including the base can have a maximum dimension of from about10 microns to about 300 microns.

Forming the drop into the first particle can include contacting the dropwith an acid. The acid can include at least one of citric acid, aceticacid, and hydrochloric acid. Contacting the drop with an acid caninclude generating a gas. The gas can include at least one of carbondioxide, ammonia, and combinations thereof.

Forming the drop into the particle can include exposing the drop to atemperature of at least about 40° C., and/or exposing the drop to anatmosphere having a pressure of less than 30 inches Hg (e.g., at mostabout 25 inches Hg, at most about 20 inches Hg, at most about 15 inchesHg, at most about 10 inches Hg, at most about five inches Hg).

In some embodiments, removing some or all of the solvent from the dropcan include exposing the drop to an atmosphere having a pressure of lessthan 30 inches Hg (e.g., at most about 25 inches Hg, at most about 20inches Hg, at most about 15 inches Hg, at most about 10 inches Hg, atmost about five inches Hg). In certain embodiments, removing some or allof the solvent from the drop can include exposing the drop to atemperature of at least about 40° C. (e.g., at least about 70° C.)and/or at most about 120° C. (e.g., at most about 70° C.).

Embodiments can include one or more of the following advantages.

The particles can be used to deliver one or more therapeutic agents to atarget site effectively and efficiently, and/or to occlude the targetsite. In certain embodiments, the particles can absorb, retain, and/ordeliver a relatively high volume of therapeutic agent. In someembodiments, the particles can be loaded with a relatively high volumeof therapeutic agent using a passive loading technique (e.g.,absorption). In certain embodiments, the particles can be used todeliver one or more therapeutic agents (e.g., proteins, DNA, RNA, genes,cells, growth hormone, insulin) that can be fragile and/or thermallysensitive, and/or that can break down when loaded into particles usingactive loading techniques.

The particles can be used to release a therapeutic agent at a specifictime and/or over a period of time. In some embodiments, the particlescan be used to deliver a metered dose of a therapeutic agent to a targetsite over a period of time. In certain embodiments, the release of atherapeutic agent from the particles can be delayed until the particleshave reached a target site. For example, the particles can include abioerodible coating that erodes during delivery, such that when theparticles reach the target site, they can begin to release thetherapeutic agent.

The particles can be relatively durable and/or flexible, and thus can beunlikely to be damaged during storage, delivery, or use. In someembodiments (e.g., embodiments in which the particles are formed ofstyrene-isobutylene-styrene), the particles can have a relatively highmechanical integrity (e.g., such that contact with the walls of acatheter will not harm the particles). In certain embodiments (e.g.,embodiments in which the particles are formed ofstyrene-isobutylene-styrene), the particles can be relatively flexible,and thus can be adapted for use in many different environments.

The particles can be used to deliver multiple therapeutic agents, eitherto the same target site, or to different target sites. For example, theparticles can deliver one type of therapeutic agent (e.g., ananti-inflammatory) as the particles are being delivered to a targetsite, and another type of therapeutic agent (e.g., a chemotherapeuticagent) once the particles have reached the target site.

Features and advantages are in the description, drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a side view of an embodiment of a particle.

FIG. 1B is a cross-sectional view of the particle of FIG. 1A, takenalong line 1B-1B.

FIG. 2 is a cross-sectional view of an embodiment of a particle.

FIG. 3A is a schematic illustrating an embodiment of injection of acomposition including particles into a vessel.

FIG. 3B is a greatly enlarged view of region 3B in FIG. 3A.

FIG. 4 is a cross-sectional view of an embodiment of a particle.

FIG. 5 is a cross-sectional view of an embodiment of a particle.

FIG. 6 is a cross-sectional view of an embodiment of a particle.

FIGS. 7A-7C are an illustration of an embodiment of a system and methodfor producing particles.

FIG. 8 is an illustration of an embodiment of a drop generator.

FIGS. 9A and 9B are an illustration of an embodiment of a system andmethod for producing particles.

FIGS. 10A-10F are an illustration of an embodiment of a system forproducing particles.

FIG. 11 is a cross-sectional view of an embodiment of a particle.

FIG. 12 is a cross-sectional view of an embodiment of a particle.

DETAILED DESCRIPTION

FIGS. 1A and 1B show a particle 100 that can be used, for example, todeliver one or more therapeutic agents to a target site within the body.Particle 100 includes a matrix 102 and pores 104. The therapeuticagent(s) can be included on particle and/or within particle 100 (e.g.,within matrix 102 and/or pores 104). In some embodiments, thetherapeutic agents can be dispersed throughout particle 100. Matrix 102of particle 100 is formed of a block copolymer that includes a firstblock having a glass transition temperature (T_(g)) of at most 37° C.and a second block having a glass transition temperature of greater than37° C.

Block copolymers are copolymers that contain two or more differingpolymer blocks selected, for example, from homopolymer blocks, copolymerblocks (e.g., random copolymer blocks, statistical copolymer blocks,gradient copolymer blocks, periodic copolymer blocks), and combinationsof homopolymer and copolymer blocks. A polymer “block” refers to agrouping of multiple copies of a single type (homopolymer block) ormultiple types (copolymer block) of constitutional units. A “chain” isan unbranched polymer block. In some embodiments, a polymer block can bea grouping of at least two (e.g., at least five, at least 10, at least20, at least 50, at least 100, at least 250, at least 500, at least 750)and/or at most 1000 (e.g., at most 750, at most 500, at most 250, atmost 100, at most 50, at most 20, at most 10, at most five) copies of asingle type or multiple types of constitutional units. A polymer blockmay take on any of a number of different architectures.

In some embodiments, the block copolymer in particle 100 can include acentral block having a glass transition temperature of at most 37° C.and end blocks each having a glass transition temperature of greaterthan 37° C. In certain embodiments, the block copolymer can have one ofthe following general structures:

-   -   (a) BAB or ABA (linear triblock),    -   (b) B(AB)_(n) or A(BA)_(n) (linear alternating block), or    -   (c) X-(AB)_(n)or X-(BA)_(n) (includes diblock, triblock and        other radial block copolymers),        where A is a block having a glass transition temperature of at        most 37° C., B is a block having a glass transition temperature        of greater than 37° C., n is a positive whole number and X is an        initiator (e.g., a monofunctional initiator, a multifunctional        initiator).

The X-(AB)_(n) structures are frequently referred to as diblockcopolymers (when n=1) or triblock copolymers (when n=2). (Thisterminology disregards the presence of the initiator, for example,treating A-X-A as a single A block with the triblock therefore denotedas BAB.) Where n=3 or more, these structures are commonly referred to asstar-shaped block copolymers.

As described above, the A blocks have a glass transition temperature ofat most 37° C. In some embodiments, the A blocks can have a glasstransition temperature of at most about 30° C. (e.g., at most about 25°C., at most about 20° C., at most about 10° C., at most about 0° C., atmost about −10° C., at most about −20° C., at most about −30° C., atmost about −50° C., at most about −70° C., at most about −90° C.). Asreferred to herein, the glass transition temperature of a material(e.g., a polymer block) is determined according to ASTM E1356. Examplesof blocks having a glass transition temperature of at most 37° C. whenthe blocks are in the dry state (e.g., in powder form) include blocksincluding at least one of the following monomers:

-   -   (1) acrylic monomers including:        -   (a) alkyl acrylates, such as methyl acrylate, ethyl            acrylate, propyl acrylate, isopropyl acrylate (e.g.,            isotactic isopropyl acrylate), butyl acrylate, sec-butyl            acrylate, isobutyl acrylate, cyclohexyl acrylate,            2-ethylhexyl acrylate, dodecyl acrylate and hexadecyl            acrylate,        -   (b) arylalkyl acrylates, such as benzyl acrylate,        -   (c) alkoxyalkyl acrylates, such as 2-ethoxyethyl acrylate            and 2-methoxyethyl acrylate,        -   (d) halo-alkyl acrylates, such as 2,2,2-trifluoroethyl            acrylate, and        -   (e) cyano-alkyl acrylates, such as 2-cyanoethyl acrylate;    -   (2) methacrylic monomers including:        -   (a) alkyl methacrylates, such as butyl methacrylate, hexyl            methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate,            dodecyl methacrylate, hexadecyl methacrylate and octadecyl            methacrylate, and        -   (b) aminoalkyl methacrylates, such as diethylaminoethyl            methacrylate and 2-tert-butyl-aminoethyl methacrylate;    -   (3) vinyl ether monomers including:        -   (a) alkyl vinyl ethers, such as methyl vinyl ether, ethyl            vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl            vinyl ether, 2-ethylhexyl vinyl ether and dodecyl vinyl            ether;    -   (4) cyclic ether monomers, such as tetrahydrofuran, trimethylene        oxide, ethylene oxide, propylene oxide, methyl glycidyl ether,        butyl glycidyl ether, allyl glycidyl ether, epibromohydrin,        epichlorohydrin, 1,2-epoxybutane, 1,2-epoxyoctane, and        1,2-epoxydecane;    -   (5) ester monomers (other than acrylates and methacrylates),        such as ethylene malonate, vinyl acetate, and vinyl propionate;    -   (6) alkene monomers, such as ethylene, propylene, isobutylene,        1-butene, trans-butadiene, 4-methyl pentene, 1-octene and other        α-olefins, cis-isoprene, and trans-isoprene;    -   (7) halogenated alkene monomers, such as vinylidene chloride,        vinylidene fluoride, cis-chlorobutadiene, and        trans-chlorobutadiene;    -   (8) siloxane monomers, such as dimethylsiloxane,        diethylsiloxane, methylethylsiloxane, methylphenylsiloxane, and        diphenylsiloxane; and    -   (9) maleic monomers, such as maleic anhydride.

In certain embodiments, the A blocks can include one or more derivativesof the above monomers.

In some embodiments, the A blocks can be based upon one or morepolyolefins. In certain embodiments, the A blocks can be polyolefinicblocks having alternating quaternary and secondary carbons of thegeneral formulation: —(CRR′—CH₂)_(n)—, where R and R′ are linear orbranched aliphatic groups (e.g., methyl, ethyl, propyl, isopropyl,butyl, isobutyl) or cyclic aliphatic groups (e.g., cyclohexane,cyclopentane), with and without pendant groups. For example, the Ablocks can be polyolefinic blocks having the above formula, in which Rand R′ are the same. As an example, the A blocks can be based onisobutylene:

(i.e., in which R and R′ are both methyl groups).

In some embodiments, the block copolymer can include at least about 40mol percent (e.g., from about 45 mol percent to about 95 mol percent) ofpolyolefin blocks.

As described above, the B blocks have a glass transition temperature ofgreater than 37° C. In some embodiments, the B blocks can have a glasstransition temperature of at least about 40° C. (e.g., at least about50° C., at least about 70° C., at least about 90° C., a least about 100°C., at least about 120° C.). Examples of blocks having a glasstransition temperature of greater than 37° C. when the blocks are in thedry state (e.g., in powder form) include blocks including at least oneof the following monomers:

-   -   (1) vinyl aromatic monomers including:        -   (a) unsubstituted vinyl aromatics, such as atactic styrene,            isotactic styrene and 2-vinyl naphthalene,        -   (b) vinyl-substituted aromatics, such as a-methyl styrene,            and        -   (c) ring-substituted vinyl aromatics including            ring-alkylated vinyl aromatics (e.g., 3-methylstyrene,            4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene,            3,5-dimethylstyrene, 2,4,6-trimethylstyrene,            4-tert-butylstyrene), ring-alkoxylated vinyl aromatics            (e.g., 4-methoxystyrene, 4-ethoxystyrene), ring-halogenated            vinyl aromatics (e.g., 2-chlorostyrene, 3-chlorostyrene,            4-chlorostyrene, 2,6-dichlorostyrene, 4-bromostyrene,            4-fluorostyrene), ring-ester-substituted vinyl aromatics            (e.g., 4-acetoxystyrene), and hydroxyl styrene;    -   (2) other vinyl monomers including:        -   (a) vinyl esters such as vinyl benzoate, vinyl 4-tert-butyl            benzoate, vinyl cyclohexanoate, vinyl pivalate, vinyl            trifluoroacetate, vinyl butyral,        -   (b) vinyl amines such as 2-vinyl pyridine, 4-vinyl pyridine,            and vinyl carbazole,        -   (c) vinyl halides such as vinyl chloride and vinyl fluoride,        -   (d) alkyl vinyl ethers such as tert-butyl vinyl ether and            cyclohexyl vinyl ether, and        -   (e) other vinyl compounds such as vinyl ferrocene;    -   (3) other aromatic monomers including acenaphthalene and indene;    -   (4) methacrylic monomers including:        -   (a) methacrylic acid anhydride,        -   (b) methacrylic acid esters (methacrylates) including            -   (i) alkyl methacrylates such as atactic methyl                methacrylate, syndiotactic methyl methacrylate, ethyl                methacrylate, isopropyl methacrylate, isobutyl                methacrylate, t-butyl methacrylate and cyclohexyl                methacrylate,            -   (ii) aromatic methacrylates such as phenyl methacrylate                and including aromatic alkyl methacrylates such as                benzyl methacrylate,            -   (iii) hydroxyalkyl methacrylates such as 2-hydroxyethyl                methacrylate and 2-hydroxypropyl methacrylate,            -   (iv) additional methacrylates including isobornyl                methacrylate and trimethylsilyl methacrylate, and        -   (c) other methacrylic-acid derivatives including            methacrylonitrile;    -   (5) acrylic monomers including:        -   (a) certain acrylic acid esters such as tert-butyl acrylate,            hexyl acrylate and isobomyl acrylate,        -   (b) other acrylic-acid derivatives including acrylonitrile;            and    -   (6) silicate monomers including polyhedral oligomeric        silsesquioxane (POSS) monomers.

In some embodiments, the B blocks can include one or more derivatives ofthe above monomers.

In certain embodiments, the B blocks can be polymers of methacrylates orpolymers of vinyl aromatics. In some embodiments, the B blocks can beeither: (a) made from monomers of styrene:

or styrene derivatives (e.g., α-methylstyrene, ring-alkylated styrenesor ring-halogenated styrenes) or mixtures thereof, or (b) made frommonomers of methylmethacrylate, ethylmethacrylate, hydroxyethylmethacrylate, or mixtures thereof.

In some embodiments, the block copolymer can include at least about fivemol percent (e.g., at least about 30 mol percent, about 60 mol percent)of styrene blocks.

An example of one of the above copolymers is styrene-isobutylene-styrene(“SIBS”), in which the A blocks are based on isobutylene, and the Bblocks are based on styrene. Another example of one of the abovecopolymers is styrene maleic anhydride (“SMA”), in which the A blocksare based on maleic anhydride and the B blocks are based on styrene.

Typically, the combined molecular weight of the block copolymer can bemore than about 40,000 Daltons (e.g., more than about 60,000 Daltons).For example, the combined molecular weight of the block copolymer can befrom about 80,000 Daltons to about 300,000 Daltons (e.g., from about90,000 Daltons to about 300,000 Daltons). In some embodiments (e.g.,embodiments in which the A blocks are polyolefin blocks), the combinedmolecular weight of the A blocks can be from about 60,000 Daltons toabout 200,000 Daltons. In certain embodiments (e.g., embodiments inwhich the B blocks are vinyl aromatic blocks), the combined molecularweight of the B blocks can be from about 20,000 Daltons to about 100,000Daltons.

Generally, the properties of the block copolymer used in particle 100can depend upon the lengths of the A block chains and B block chains inthe block copolymer, and/or on the relative amounts of A block and Bblocks in the block copolymer.

As an example, in some embodiments, blocks with a glass transitiontemperature of at most 37° C. may be elastomeric. In such embodiments,the elastomeric properties of the block copolymer can depend on thelength of the A block chains. In certain embodiments, the A block chainscan have a weight average molecular weight of from about 2,000 Daltonsto about 30,000 Daltons. In such embodiments, the block copolymer and/orparticle 100 may be relatively inelastic. In some embodiments, the Ablock chains can have a weight average molecular weight of at leastabout 40,000 Daltons. In such embodiments, the block copolymer and/orparticle 100 may be relatively soft and/or rubbery.

As another example, in certain embodiments, blocks with a glasstransition temperature of greater than 37° C. may be relatively hard at37° C. In such embodiments, the hardness of the block copolymer at 37°C. can depend on the relative amount of B blocks in the block copolymer.In some embodiments, the block copolymer can have a hardness of fromabout Shore 20 A to about Shore 75 D (e.g., from about Shore 40 A toabout Shore 90A). In certain embodiments, a copolymer with a desireddegree of hardness may be formed by varying the proportions of the A andB blocks in the copolymer, with a lower relative proportion of B blocksresulting in a copolymer of lower hardness, and a higher relativeproportion of B blocks resulting in a copolymer of higher hardness. As aspecific example, high molecular weight (i.e., greater than 100,000Daltons) polyisobutylene is a relatively soft and gummy material with aShore hardness of approximately 10 A. By comparison, polystyrene is muchharder, typically having a Shore hardness on the order of 100 D. As aresult, when blocks of polyisobutylene and styrene are combined, theresulting copolymer can have a range of hardnesses from as soft as Shore10 A to as hard as Shore 100 D, depending upon the relative amounts ofpolystyrene and polyisobutylene in the copolymer. In some embodiments,from about two mol percent to about 25 mol percent (e.g., from aboutfive mol percent to about 20 mol percent) of polystyrene can be used toform a block copolymer with a hardness of from about Shore 30 A to aboutShore 90 A (e.g., from about Shore 35 A to about Shore 70A).

Polydispersity (the ratio of weight average molecular weight to numberaverage molecular weight) gives an indication of the molecular weightdistribution of the copolymer, with values significantly greater thanfour indicating a broad molecular weight distribution. When allmolecules within a sample are the same size, the polydispersity has avalue of one. Typically, copolymers used in particle 100 can have arelatively tight molecular weight distribution, with a polydispersity offrom about 1.1 to about 1.7.

In some embodiments, one or more of the above-described copolymers canhave a relatively high tensile strength. For example, triblockcopolymers of polystyrene-polyisobutylene-polystyrene can have a tensilestrength of at least about 2,000 psi (e.g., from about 2,000 psi toabout 4,000 psi).

In certain embodiments, one or more of the above-described copolymerscan be relatively resistant to cracking and/or other forms ofdegradation under in vivo conditions. Additionally or alternatively, oneor more of the above-described polymers can exhibit excellentbiocompatibility, including vascular compatibility. For example, thepolymers can provoke minimal adverse tissue reactions, resulting inreduced polymorphonuclear leukocyte and reduced macrophage activity. Insome embodiments, one or more of the above-described polymers cangenerally be hemocompatible, and can thereby minimize thromboticocclusion of, for example, small vessels.

The above-described block copolymers can be made using any appropriatemethod known in the art. In some embodiments, the block copolymers canbe made by a carbocationic polymerization process that includes aninitial polymerization of a monomer or mixtures of monomers to form theA blocks, followed by the subsequent addition of a monomer or a mixtureof monomers capable of forming the B blocks. Such polymerizationreactions are described, for example, in Kennedy et al., U.S. Pat. No.4,276,394; Kennedy, U.S. Pat. No. 4,316,973; Kennedy, U.S. Pat. No.4,342,849; Kennedy et al., U.S. Pat. No. 4,910,321; Kennedy et al., U.S.Pat. No. 4,929,683; Kennedy et al., U.S. Pat. No. 4,946,899; Kennedy etal., U.S. Pat. No. 5,066,730; Kennedy et al., U.S. Pat. No. 5,122,572;and Kennedy et al., U.S. Pat. No. Re. 34,640. Each of these patents isincorporated herein by reference.

The techniques disclosed in these patents generally involve an“initiator”, which can be used to create X-(AB)_(n) structures, where Xis the initiator, and n can be 1, 2, 3 or more. The initiator can bemonofunctional or multifunctional. As noted above, the resultingmolecules are referred to as diblock copolymers where n is 1, triblockcopolymers (disregarding the presence of the initiator) where n is 2,and star-shaped block copolymers where n is 3 or more.

In general, the polymerization reaction can be conducted underconditions that minimize or avoid chain transfer and termination of thegrowing polymer chains. Steps can be taken to keep active hydrogen atoms(water, alcohol and the like) to a minimum. The temperature for thepolymerization is usually from about −10° C. to about −90° C. (e.g.,from about −60° C. to about −80° C.), although lower temperatures can beused.

Typically, one or more A blocks (e.g., polyisobutylene blocks) can beformed in a first step, followed by the addition of B blocks (e.g.,polystyrene blocks) at the ends of the A blocks. More particularly, thefirst polymerization step is generally carried out in an appropriatesolvent system, such as a mixture of polar and non-polar solvents (e.g.,methyl chloride and hexanes). The reaction bath can contain theaforementioned solvent system, olefin monomer (e.g., isobutylene), aninitiator (e.g., a tert-ester, tert-ether, tert-hydroxyl or tert-halogencontaining compound, a cumyl ester of a hydrocarbon acid, an alkyl cumylether, a cumyl halide, a cumyl hydroxyl compound, or a hindered versionof the above), and a coinitiator (e.g., a Lewis acid, such as borontrichloride or titanium tetrachloride). In some embodiments, electronpair donors (e.g., dimethyl acetamide, dimethyl sulfoxide, dimethylphthalate) can be added to the solvent system. Additionally,proton-scavengers that scavenge water, such as2,6-di-tert-butylpyridine, 4-methyl-2,6-di-tert-butylpyridine,1,8-bis(dimethylamino)-naphthalene, or diisopropylethyl amine can beadded.

The reaction is commenced by removing the tert-ester, tert-ether,tert-hydroxyl or tert-halogen (herein called the “tert-leaving groups”)from the initiator by reacting the initiator with the Lewis acid. Inplace of the tert-leaving groups is a quasi-stable or “living” cationwhich is stabilized by the surrounding tertiary carbons, as well as thepolar solvent system and electron pair donors. After obtaining thecation, the A block monomer (e.g., isobutylene) is introduced, andcationically propagates or polymerizes from each cation on theinitiator. When the A block is polymerized, the propagated cationsremain on the ends of the A blocks. The B block monomer (e.g., styrene)is then introduced, and polymerizes and propagates from the ends of theA block. Once the B blocks are polymerized, the reaction is terminatedby adding a termination molecule such as methanol, water and the like.

Product molecular weights are generally determined by reaction time,reaction temperature, the nature and concentration of the reactants, andso forth. Consequently, different reaction conditions may producedifferent products. In general, synthesis of the desired reactionproduct is achieved by an iterative process in which the course of thereaction is monitored by the examination of samples taken periodicallyduring the reaction—a technique widely employed in the art. To achievethe desired product, an additional reaction may be required in whichreaction time and temperature, reactant concentration, and so forth arechanged.

Additional details regarding cationic processes for making copolymersare found, for example, in Kennedy et al., U.S. Pat. No. 4,276,394;Kennedy, U.S. Pat. No. 4,316,973; Kennedy, U.S. Pat. No. 4,342,849;Kennedy et al., U.S. Pat. No. 4,910,321; Kennedy et al., U.S. Pat. No.4,929,683; Kennedy et al., U.S. Pat. No. 4,946,899; Kennedy et al., U.S.Pat. No. 5,066,730; Kennedy et al., U.S. Pat. No. 5,122,572; and Kennedyet al., U.S. Pat. No. Re. 34,640, incorporated supra.

The block copolymer may be recovered from the reaction mixture by any ofthe usual techniques including evaporation of solvent, precipitationwith a non-solvent such as an alcohol or alcohol/acetone mixture,followed by drying, and so forth. In addition, purification of thecopolymer can be performed by sequential extraction in aqueous media,both with and without the presence of various alcohols, ethers andketones.

In some embodiments, matrix 102 can be formed of a block copolymer thatincludes one or more functional groups. The functional groups can benegatively charged or positively charged, and/or can be ionically bondedto the polymer. In some embodiments, the functional groups can enhancethe biocompatibility of the polymer. Alternatively or additionally, thefunctional groups can enhance the clot-forming capabilities of thepolymer. Examples of functional groups include phosphate groups,carboxylate groups, sulfonate groups, sulfate groups, phosphonategroups, and phenolate groups. For example, a polymer can be a sulfonatedstyrenic polymer, such as sulfonated SIBS. Sulfonation of styrene blockcopolymers is disclosed, for example, in Ehrenberg, et al., U.S. Pat.No. 5,468,574; Vachon et al., U.S. Pat. No. 6,306,419; andBerlowitz-Tarrant, et al., U.S. Pat. No. 5,840,387, all of which areincorporated herein by reference. Examples of other functionalizedpolymers include phosphated SIBS and carboxylated SIBS. In certainembodiments, a polymer can include more than one different type offunctional group. For example, a polymer can include both a sulfonategroup and a phosphate group. In some embodiments, a polymer thatincludes a functional group can be reacted with a cross-linking and/orgelling agent during particle formation. For example, a particle thatincludes a sulfonates group, such as sulfonated SIBS, may be reactedwith a cross-linking and/or gelling agent such as calcium chloride.Functionalized polymers and cross-linking and/or gelling agents aredescribed, for example, in Richard et al., U.S. patent application Ser.No. 10/927,868, filed on Aug. 27, 2004, and entitled “Embolization”,which is incorporated herein by reference.

The presence of pores 104 in particle 100 can enhance the ability ofparticle 100 to retain a relatively high volume of therapeutic agent. Insome embodiments, as the sizes of pores 104 increase, the volume oftherapeutic agent retained by particle 100 can increase. In certainembodiments, one or more of pores 104 can have a maximum dimension of atleast 0.01 micron (e.g., at least 0.05 micron, at least about 0.1micron, at least about 0.5 micron, at least about one micron, at leastabout five microns, at least about 10 microns, at least about 15microns, at least about 20 microns, at least about 25 microns, at leastabout 30 microns, at least about 35 microns, at least about 50 microns,at least about 100 microns, at least about 150 microns, at least about200 microns, at least about 250 microns), and/or at most about 300microns (e.g., at most about 250 microns, at most about 200 microns, atmost about 150 microns, at most about 100 microns, at most about 50microns, at most about 35 microns, at most about 30 microns, at mostabout 25 microns, at most about 20 microns, at most about 15 microns, atmost about 10 microns, at most about five microns, at most about onemicron, at most about 0.5 micron, at most about 0.1 micron, at mostabout 0.05 micron). In some embodiments, some or all of pores 104 canhave a maximum dimension of from 0.01 micron to about one micron, and/orsome or all of pores 104 can have a maximum dimension of from about 10microns to about 300 microns (e.g., from about 100 microns to about 300microns).

In certain embodiments, the pores in a particle can form a porositygradient. The porosity gradient can be used, for example, the regulatethe delivery of therapeutic agent from a particle.

As an example, FIG. 2 shows a particle 150 formed of a block copolymermatrix 151. Particle 150 includes a center region, C, from the center c′of particle 150 to a radius of about r/3, a body region, B, from aboutr/3 to about 2r/3, and a surface region, S, from about 2r/3 to r. Ingeneral, the mean size of the pores in region C of particle 150 isgreater than the mean size of the pores at region S of particle 150. Incertain embodiments, the mean size of the pores in region C of particle150 is greater than the mean size of the pores in region B particle 150,and/or the mean size of the pores in region B of particle 150 is greaterthan the mean size of the pores at region S of particle 150.

For example, region C of particle 150 includes relatively large pores152. In some embodiments, relatively large pores 152 can have a meandiameter of about 20 microns or more (e.g., about 30 microns or more,from about 20 microns to about 35 microns). Region B of particle 150includes intermediate-sized pores 154. In certain embodiments,intermediate-sized pores 154 can have a mean diameter of about 18microns or less (e.g. about 15 microns or less, from about two micronsto about 18 microns). Region S of particle 150 includes relatively smallpores 156. In some embodiments, relatively small pores 156 can have amean diameter of one micron or less (e.g. from 0.01 micron to about 0.1micron).

In certain embodiments, the density of pores (the number of pores perunit volume) at region S of particle 150 can be greater than the densityof pores in region C of particle 150. In some embodiments, the densityof pores at region S of particle 150 can be greater than the density ofpores in region B of particle 150, and/or the density of pores in regionB of particle 150 can be greater than the density of pores in region Cof particle 150.

While FIGS. 1B and 2 show particles with pores having different sizes,in some embodiments, a particle can include pores that have the samesize (e.g., that have the same diameter).

As described above, particle 100 can be used to deliver one or moretherapeutic agents (e.g., a combination of therapeutic agents) to atarget site. In some embodiments, a therapeutic agent can behydrophilic. In certain embodiments, a therapeutic agent can belipophilic. Therapeutic agents include genetic therapeutic agents,non-genetic therapeutic agents, and cells, and can be negativelycharged, positively charged, amphoteric, or neutral. Therapeutic agentscan be, for example, materials that are biologically active to treatphysiological conditions; pharmaceutically active compounds; proteins;gene therapies; nucleic acids with and without carrier vectors (e.g.,recombinant nucleic acids, DNA (e.g., naked DNA), cDNA, RNA, genomicDNA, cDNA or RNA in a non-infectious vector or in a viral vector whichmay have attached peptide targeting sequences, antisense nucleic acids(RNA, DNA)); oligonucleotides; gene/vector systems (e.g., anything thatallows for the uptake and expression of nucleic acids); DNA chimeras(e.g., DNA chimeras which include gene sequences and encoding for ferryproteins such as membrane translocating sequences (“MTS”) and herpessimplex virus-1 (“VP22”)); compacting agents (e.g., DNA compactingagents); viruses; polymers; hyaluronic acid; proteins (e.g., enzymessuch as ribozymes, asparaginase); immunologic species; nonsteroidalanti-inflammatory medications; oral contraceptives; progestins;gonadotrophin-releasing hormone agonists; chemotherapeutic agents; andradioactive species (e.g., radioisotopes, radioactive molecules).Non-limiting examples of therapeutic agents include anti-thrombogenicagents; antioxidants; angiogenic and anti-angiogenic agents and factors;anti-proliferative agents (e.g., agents capable of blocking smoothmuscle cell proliferation, such as rapamycin); calcium entry blockers(e.g., verapamil, diltiazem, nifedipine); and survival genes whichprotect against cell death (e.g., anti-apoptotic Bcl-2 family factorsand Akt kinase).

Exemplary non-genetic therapeutic agents include: anti-thrombotic agentssuch as heparin, heparin derivatives, urokinase, and PPack(dextrophenylalanine proline arginine chloromethylketone);anti-inflammatory agents such as dexamethasone, prednisolone,corticosterone, budesonide, estrogen, acetyl salicylic acid,sulfasalazine and mesalamine;antineoplastic/antiproliferative/anti-mitotic agents such as paclitaxel,5-fluorouracil, cisplatin, methotrexate, doxorubicin, vinblastine,vincristine, epothilones, endostatin, angiostatin, angiopeptin,monoclonal antibodies capable of blocking smooth muscle cellproliferation, and thymidine kinase inhibitors; anesthetic agents suchas lidocaine, bupivacaine and ropivacaine; anti-coagulants such asD-Phe-Pro-Arg chloromethyl ketone, an RGD peptide-containing compound,heparin, hirudin, antithrombin compounds, platelet receptor antagonists,anti-thrombin antibodies, anti-platelet receptor antibodies, aspirin,prostaglandin inhibitors, platelet inhibitors and tick antiplateletfactors or peptides; vascular cell growth promoters such as growthfactors, transcriptional activators, and translational promoters;vascular cell growth inhibitors such as growth factor inhibitors (e.g.,PDGF inhibitor-Trapidil), growth factor receptor antagonists,transcriptional repressors, translational repressors, replicationinhibitors, inhibitory antibodies, antibodies directed against growthfactors, bifunctional molecules consisting of a growth factor and acytotoxin, bifunctional molecules consisting of an antibody and acytotoxin; protein kinase and tyrosine kinase inhibitors (e.g.,tyrphostins, genistein, quinoxalines); prostacyclin analogs;cholesterol-lowering agents; angiopoietins; antimicrobial agents such astriclosan, cephalosporins, aminoglycosides and nitrofurantoin; cytotoxicagents, cytostatic agents and cell proliferation affectors; vasodilatingagents; and agents that interfere with endogenous vasoactive mechanisms.

Exemplary genetic therapeutic agents include: anti-sense DNA and RNA;DNA coding for anti-sense RNA, tRNA or rRNA to replace defective ordeficient endogenous molecules, angiogenic factors including growthfactors such as acidic and basic fibroblast growth factors, vascularendothelial growth factor, epidermal growth factor, transforming growthfactor α and β, platelet-derived endothelial growth factor,platelet-derived growth factor, tumor necrosis factor a, hepatocytegrowth factor, and insulin like growth factor, cell cycle inhibitorsincluding CD inhibitors, thymidine kinase (“TK”) and other agents usefulfor interfering with cell proliferation, and the family of bonemorphogenic proteins (“BMP's”), including BMP2, BMP3, BMP4, BMP5, BMP6(Vgr1), BMP7 (OP1), BMP8, BMP9, BMP10, BM 11, BMP12, BMP13, BMP14,BMP15, and BMP16. Currently preferred BMP's are any of BMP2, BMP3, BMP4,BMP5, BMP6 and BMP7. These dimeric proteins can be provided ashomodimers, heterodimers, or combinations thereof, alone or togetherwith other molecules. Alternatively or additionally, molecules capableof inducing an upstream or downstream effect of a BMP can be provided.Such molecules include any of the “hedgehog” proteins, or the DNA'sencoding them. Vectors of interest for delivery of genetic therapeuticagents include: plasmids; viral vectors such as adenovirus (AV),adenoassociated virus (AAV) and lentivirus; and non-viral vectors suchas lipids, liposomes and cationic lipids.

Cells include cells of human origin (autologous or allogeneic),including stem cells, or from an animal source (xenogeneic), which canbe genetically engineered if desired to deliver proteins of interest.

Several of the above and numerous additional therapeutic agentsappropriate for the practice of the present invention are disclosed inKunz et al., U.S. Pat. No. 5,733,925, assigned to NeoRx Corporation,which is incorporated herein by reference. Therapeutic agents disclosedin this patent include the following:

“Cytostatic agents” (i.e., agents that prevent or delay cell division inproliferating cells, for example, by inhibiting replication of DNA or byinhibiting spindle fiber formation). Representative examples ofcytostatic agents include modified toxins, methotrexate, adriamycin,radionuclides (e.g., such as disclosed in Fritzberg et al., U.S. Pat.No. 4,897,255), protein kinase inhibitors, including staurosporin, aprotein kinase C inhibitor of the following formula:

as well as diindoloalkaloids having one of the following generalstructures:

as well as stimulators of the production or activation of TGF-beta,including Tamoxifen and derivatives of functional equivalents (e.g.,plasmin, heparin, compounds capable of reducing the level orinactivating the lipoprotein Lp(a) or the glycoproteinapolipoprotein(a)) thereof, TGF-beta or functional equivalents,derivatives or analogs thereof, suramin, nitric oxide releasingcompounds (e.g., nitroglycerin) or analogs or functional equivalentsthereof, paclitaxel or analogs thereof (e.g., taxotere), inhibitors ofspecific enzymes (such as the nuclear enzyme DNA topoisomerase II andDNA polymerase, RNA polymerase, adenyl guanyl cyclase), superoxidedismutase inhibitors, terminal deoxynucleotidyl-transferase, reversetranscriptase, antisense oligonucleotides that suppress smooth musclecell proliferation and the like. Other examples of “cytostatic agents”include peptidic or mimetic inhibitors (i.e., antagonists, agonists, orcompetitive or non-competitive inhibitors) of cellular factors that may(e.g., in the presence of extracellular matrix) trigger proliferation ofsmooth muscle cells or pericytes: e.g., cytokines (e.g., interleukinssuch as IL-1), growth factors (e.g., PDGF, TGF-alpha or -beta, tumornecrosis factor, smooth muscle- and endothelial-derived growth factors,i.e., endothelin, FGF), homing receptors (e.g., for platelets orleukocytes), and extracellular matrix receptors (e.g., integrins).Representative examples of useful therapeutic agents in this category ofcytostatic agents addressing smooth muscle proliferation include:subfragments of heparin, triazolopyrimidine (trapidil; a PDGFantagonist), lovastatin, and prostaglandins E1 or I2.

Agents that inhibit the intracellular increase in cell volume (i.e., thetissue volume occupied by a cell), such as cytoskeletal inhibitors ormetabolic inhibitors. Representative examples of cytoskeletal inhibitorsinclude colchicine, vinblastin, cytochalasins, paclitaxel and the like,which act on microtubule and microfilament networks within a cell.Representative examples of metabolic inhibitors include staurosporin,trichothecenes, and modified diphtheria and ricin toxins, Pseudomonasexotoxin and the like. Trichothecenes include simple trichothecenes(i.e., those that have only a central sesquiterpenoid structure) andmacrocyclic trichothecenes (i.e., those that have an additionalmacrocyclic ring), e.g., a verrucarins or roridins, including VerrucarinA, Verrucarin B, Verrucarin J (Satratoxin C), Roridin A, Roridin C,Roridin D, Roridin E (Satratoxin D), Roridin H.

Agents acting as an inhibitor that blocks cellular protein synthesisand/or secretion or organization of extracellular matrix (i.e., an“anti-matrix agent”). Representative examples of “anti-matrix agents”include inhibitors (i.e., agonists and antagonists and competitive andnon-competitive inhibitors) of matrix synthesis, secretion and assembly,organizational cross-linking (e.g., transglutaminases cross-linkingcollagen), and matrix remodeling (e.g., following wound healing). Arepresentative example of a useful therapeutic agent in this category ofanti-matrix agents is colchicine, an inhibitor of secretion ofextracellular matrix. Another example is tamoxifen for which evidenceexists regarding its capability to organize and/or stabilize as well asdiminish smooth muscle cell proliferation following angioplasty. Theorganization or stabilization may stem from the blockage of vascularsmooth muscle cell maturation in to a pathologically proliferating form.

Agents that are cytotoxic to cells, particularly cancer cells. Preferredagents are Roridin A, Pseudomonas exotoxin and the like or analogs orfunctional equivalents thereof. A plethora of such therapeutic agents,including radioisotopes and the like, have been identified and are knownin the art. In addition, protocols for the identification of cytotoxicmoieties are known and employed routinely in the art.

A number of the above therapeutic agents and several others have alsobeen identified as candidates for vascular treatment regimens, forexample, as agents targeting restenosis. Such agents include one or moreof the following: calcium-channel blockers, including benzothiazapines(e.g., diltiazem, clentiazem); dihydropyridines (e.g., nifedipine,amlodipine, nicardapine); phenylalkylamines (e.g., verapamil); serotoninpathway modulators, including 5-HT antagonists (e.g., ketanserin,naftidrofuryl) and 5-HT uptake inhibitors (e.g., fluoxetine); cyclicnucleotide pathway agents, including phosphodiesterase inhibitors (e.g.,cilostazole, dipyridamole), adenylate/guanylate cyclase stimulants(e.g., forskolin), and adenosine analogs; catecholamine modulators,including α-antagonists (e.g., prazosin, bunazosine), β-antagonists(e.g., propranolol), and α/β-antagonists (e.g., labetalol, carvedilol);endothelin receptor antagonists; nitric oxide donors/releasingmolecules, including organic nitrates/nitrites (e.g., nitroglycerin,isosorbide dinitrate, amyl nitrite), inorganic nitroso compounds (e.g.,sodium nitroprusside), sydnonimines (e.g., molsidomine, linsidomine),nonoates (e.g., diazenium diolates, NO adducts of alkanediamines),S-nitroso compounds, including low molecular weight compounds (e.g.,S-nitroso derivatives of captopril, glutathione and N-acetylpenicillamine) and high molecular weight compounds (e.g., S-nitrosoderivatives of proteins, peptides, oligosaccharides, polysaccharides,synthetic polymers/oligomers and natural polymers/oligomers),C-nitroso-, O-nitroso- and N-nitroso-compounds, and L-arginine; ACEinhibitors (e.g., cilazapril, fosinopril, enalapril); ATII-receptorantagonists (e.g., saralasin, losartin); platelet adhesion inhibitors(e.g., albumin, polyethylene oxide); platelet aggregation inhibitors,including aspirin and thienopyridine (ticlopidine, clopidogrel) and GPIIb/IIIa inhibitors (e.g., abciximab, epitifibatide, tirofiban,intergrilin); coagulation pathway modulators, including heparinoids(e.g., heparin, low molecular weight heparin, dextran sulfate,β-cyclodextrin tetradecasulfate), thrombin inhibitors (e.g., hirudin,hirulog, PPACK (D-phe-L-propyl-L-arg-chloromethylketone), argatroban),FXa inhibitors (e.g., antistatin, TAP (tick anticoagulant peptide)),vitamin K inhibitors (e.g., warfarin), and activated protein C;cyclooxygenase pathway inhibitors (e.g., aspirin, ibuprofen,flurbiprofen, indomethacin, sulfinpyrazone); natural and syntheticcorticosteroids (e.g., dexamethasone, prednisolone, methprednisolone,hydrocortisone); lipoxygenase pathway inhibitors (e.g.,nordihydroguairetic acid, caffeic acid; leukotriene receptorantagonists; antagonists of E- and P-selectins; inhibitors of VCAM-1 andICAM-1 interactions; prostaglandins and analogs thereof, includingprostaglandins such as PGE1 and PGI2; prostacyclins and prostacyclinanalogs (e.g., ciprostene, epoprostenol, carbacyclin, iloprost,beraprost); macrophage activation preventers (e.g., bisphosphonates);HMG-CoA reductase inhibitors (e.g., lovastatin, pravastatin,fluvastatin, simvastatin, cerivastatin); fish oils and omega-3-fattyacids; free-radical scavengers/antioxidants (e.g., probucol, vitamins Cand E, ebselen, retinoic acid (e.g., trans-retinoic acid), SOD mimics);agents affecting various growth factors including FGF pathway agents(e.g., bFGF antibodies, chimeric fusion proteins), PDGF receptorantagonists (e.g., trapidil), IGF pathway agents (e.g., somatostatinanalogs such as angiopeptin and ocreotide), TGF-β pathway agents such aspolyanionic agents (heparin, fucoidin), decorin, and TGF-62 antibodies,EGF pathway agents (e.g., EGF antibodies, receptor antagonists, chimericfusion proteins), TNF-α pathway agents (e.g., thalidomide and analogsthereof), thromboxane A2 (TXA2) pathway modulators (e.g., sulotroban,vapiprost, dazoxiben, ridogrel), protein tyrosine kinase inhibitors(e.g., tyrphostin, genistein, and quinoxaline derivatives); MMP pathwayinhibitors (e.g., marimastat, ilomastat, metastat), and cell motilityinhibitors (e.g., cytochalasin B); antiproliferative/antineoplasticagents including antimetabolites such as purine analogs (e.g.,6-mercaptopurine), pyrimidine analogs (e.g., cytarabine and5-fluorouracil) and methotrexate, nitrogen mustards, alkyl sulfonates,ethylenimines, antibiotics (e.g., daunorubicin, doxorubicin, daunomycin,bleomycin, mitomycin, penicillins, cephalosporins, ciprofalxin,vancomycins, aminoglycosides, quinolones, polymyxins, erythromycins,tertacyclines, chloramphenicols, clindamycins, linomycins, sulfonamides,and their homologs, analogs, fragments, derivatives, and pharmaceuticalsalts), nitrosoureas (e.g., carmustine, lomustine) and cisplatin, agentsaffecting microtubule dynamics (e.g., vinblastine, vincristine,colchicine, paclitaxel, epothilone), caspase activators, proteasomeinhibitors, angiogenesis inhibitors (e.g., endostatin, angiostatin andsqualamine), and rapamycin, cerivastatin, flavopiridol and suramin;matrix deposition/organization pathway inhibitors (e.g., halofuginone orother quinazolinone derivatives, tranilast); endothelializationfacilitators (e.g., VEGF and RGD peptide); and blood rheology modulators(e.g., pentoxifylline).

Other examples of therapeutic agents include anti-tumor agents, such asdocetaxel, alkylating agents (e.g., mechlorethamine, chlorambucil,cyclophosphamide, melphalan, ifosfamide), plant alkaloids (e.g.,etoposide), inorganic ions (e.g., cisplatin), biological responsemodifiers (e.g., interferon), and hormones (e.g., tamoxifen, flutamide),as well as their homologs, analogs, fragments, derivatives, andpharmaceutical salts.

Additional examples of therapeutic agents include organic-solubletherapeutic agents, such as mithramycin, cyclosporine, and plicamycin.Further examples of therapeutic agents include pharmaceutically activecompounds, anti-sense genes, viral, liposomes and cationic polymers(e.g., selected based on the application), biologically active solutes(e.g., heparin), prostaglandins, prostcyclins, L-arginine, nitric oxide(NO) donors (e.g., lisidomine, molsidomine, NO-protein adducts,NO-polysaccharide adducts, polymeric or oligomeric NO adducts orchemical complexes), enoxaparin, Warafin sodium, dicumarol, interferons,interleukins, chymase inhibitors (e.g., Tranilast), ACE inhibitors(e.g., Enalapril), serotonin antagonists, 5-HT uptake inhibitors, andbeta blockers, and other antitumor and/or chemotherapy drugs, such asBiCNU, busulfan, carboplatinum, cisplatinum, cytoxan, DTIC, fludarabine,mitoxantrone, velban, VP-16, herceptin, leustatin, navelbine, rituxan,and taxotere.

Therapeutic agents are described, for example, in DiMatteo et al., U.S.Patent Application Publication No. US 2004/0076582 A1, published on Apr.22, 2004, and entitled “Agent Delivery Particle”, and in Schwarz et al.,U.S. Pat. No. 6,368,658, both of which are incorporated herein byreference.

In certain embodiments, in addition to or as an alternative to includingtherapeutic agents, particle 100 can include one or more radiopaquematerials, materials that are visible by magnetic resonance imaging(MRI-visible materials), ferromagnetic materials, and/or contrast agents(e.g., ultrasound contrast agents). Radiopaque materials, MRI-visiblematerials, ferromagnetic materials, and contrast agents are described,for example, in Rioux et al., U.S. Patent Application Publication No. US2004/0101564 A1, published on May 27, 2004, and entitled “Embolization”,which is incorporated herein by reference.

In general, particle 100 can have a diameter of about 3,000 microns orless (e.g., from about two microns to about 3,000 microns, from about 10microns to about 3,000 microns, from about 40 microns to about 2,000microns; from about 100 microns to about 700 microns; from about 500microns to about 700 microns; from about 100 microns to about 500microns; from about 100 microns to about 300 microns; from about 300microns to about 500 microns; from about 500 microns to about 1,200microns; from about 500 microns to about 700 microns; from about 700microns to about 900 microns; from about 900 microns to about 1,200microns, from about 1,000 microns to about 1,200 microns). In someembodiments, particle 100 can have a diameter of about 3,000 microns orless (e.g., about 2,500 microns or less; about 2,000 microns or less;about 1,500 microns or less; about 1,200 microns or less; about 1,150microns or less; about 1,100 microns or less; about 1,090 microns orless; about 1,080 microns or less; about 1,070 microns or less; about1,060 microns or less; about 1,050 microns or less; about 1,040 micronsor less; about 1,030 microns or less; about 1,020 microns or less; about1,010 microns or less; about 1,000 microns or less; about 900 microns orless; about 700 microns or less; about 500 microns or less; about 400microns or less; about 300 microns or less; about 100 microns or less;about 50 microns or less; about 10 microns or less; about five micronsor less) and/or about one micron or more (e.g., about five microns ormore; about 10 microns or more; about 50 microns or more; about 100microns or more; about 300 microns or more; about 400 microns or more;about 500 microns or more; about 700 microns or more; about 900 micronsor more; about 1,000 microns or more; about 1,010 microns or more; about1,020 microns or more; about 1,030 microns or more; about 1,040 micronsor more; about 1,050 microns or more; about 1,060 microns or more; about1,070 microns or more; about 1,080 microns or more; about 1,090 micronsor more; about 1,100 microns or more; about 1,150 microns or more; about1,200 microns or more; about 1,500 microns or more; about 2,000 micronsor more; about 2,500 microns or more). In some embodiments, particle 100can have a diameter of less than about 100 microns (e.g., less thanabout 50 microns).

In some embodiments, particle 100 can be substantially spherical. Incertain embodiments, particle 100 can have a sphericity of about 0.8 ormore (e.g., about 0.85 or more, about 0.9 or more, about 0.95 or more,about 0.97 or more). Particle 100 can be, for example, manuallycompressed, essentially flattened, while wet to about 50 percent or lessof its original diameter and then, upon exposure to fluid, regain asphericity of about 0.8 or more (e.g., about 0.85 or more, about 0.9 ormore, about 0.95 or more, about 0.97 or more). The sphericity of aparticle can be determined using a Beckman Coulter RapidVUE ImageAnalyzer version 2.06 (Beckman Coulter, Miami, Fla.). Briefly, theRapidVUE takes an image of continuous-tone (gray-scale) form andconverts it to a digital form through the process of sampling andquantization. The system software identifies and measures particles inan image in the form of a fiber, rod or sphere. The sphericity of aparticle, which is computed as Da/Dp (where Da=√(4A/π); Dp=P/π; A=pixelarea; P=pixel perimeter), is a value from zero to one, with onerepresenting a perfect circle.

Matrix 102 can include one or more of the block copolymers describedabove. In some embodiments, matrix 102 can include multiple (e.g., two,three, four, five, six, seven, eight, nine, 10) different blockcopolymers. For example, in some embodiments, a particle can include ablend of at least two different block copolymers. Alternatively oradditionally, matrix 102 can include other types of materials, such asother polymers that are not block copolymers. Examples of polymersinclude polyvinyl alcohols (“PVA”), polyacrylic acids, polymethacrylicacids, poly vinyl sulfonates, carboxymethyl celluloses, hydroxyethylcelluloses, substituted celluloses, polyacrylamides, polyethyleneglycols, polyamides, polyureas, polyurethanes, polyesters, polyethers,polystyrenes, polysaccharides, polylactic acids, polyethylenes,polyolefins, polypropylenes, polymethylmethacrylates, polycaprolactones,polyglycolic acids, poly(lactic-co-glycolic) acids (e.g.,poly(d-lactic-co-glycolic) acids), polysulfones, polyethersulfones,polycarbonates, nylons, silicones, linear or crosslinked polysilicones,and copolymers or mixtures thereof. In certain embodiments, matrix 102can include a highly water insoluble, high molecular weight polymer. Anexample of such a polymer is a high molecular weight PVA that has beenacetalized. Matrix 102 can include substantially pure intrachain1,3-acetalized PVA, and can be substantially free of animal derivedresidue such as collagen. In some embodiments, matrix 102 can include aminor amount (e.g., about 2.5 weight percent or less, about one weightpercent or less, about 0.2 weight percent or less) of a gelling material(e.g., a polysaccharide, such as alginate). In certain embodiments,matrix 102 can include a bioabsorbable (e.g., resorbable) polymer (e.g.,alginate, gelatin, albumin, resorbable polyvinyl alcohol, albumin,dextran, starch, ethyl cellulose, polyglycolic acid, polylactic acid,polylactic acid/polyglycolic acid copolymers, poly(lactic-co-glycolic)acid). Matrix 102 can include, for example, polyvinyl alcohol, alginate,or both polyvinyl alcohol and alginate.

In some embodiments, in addition to or as an alternative to being usedto deliver a therapeutic agent to a target site, particle 100 can beused to embolize a target site (e.g., a lumen of a subject). Forexample, multiple particles can be combined with a carrier fluid (e.g.,a pharmaceutically acceptable carrier, such as a saline solution, acontrast agent, or both) to form a composition, which can then bedelivered to a site and used to embolize the site. FIGS. 3A and 3Billustrate the use of a composition including particles to embolize alumen of a subject. As shown, a composition, including particles 100 anda carrier fluid, is injected into a vessel through an instrument such asa catheter 1150. Catheter 1150 is connected to a syringe barrel 1110with a plunger 1160. Catheter 1150 is inserted, for example, into afemoral artery 1120 of a subject. Catheter 1150 delivers the compositionto, for example, occlude a uterine artery 1130 leading to a fibroid1140. Fibroid 1140 is located in the uterus of a female subject. Thecomposition is initially loaded into syringe 1110. Plunger 1160 ofsyringe 1110 is then compressed to deliver the composition throughcatheter 1150 into a lumen 1165 of uterine artery 1130.

FIG. 3B, which is an enlarged view of section 3B of FIG. 3A, shows auterine artery 1130 that is subdivided into smaller uterine vessels 1170(e.g., having a diameter of about two millimeters or less) which feedfibroid 1140. The particles 100 in the composition partially or totallyfill the lumen of uterine artery 1130, either partially or completelyoccluding the lumen of the uterine artery 1130 that feeds uterinefibroid 1140.

Compositions that include particles such as particles 100 can bedelivered to various sites in the body, including, for example, siteshaving cancerous lesions, such as the breast, prostate, lung, thyroid,or ovaries. The compositions can be used in, for example, neural,pulmonary, and/or AAA (abdominal aortic aneurysm) applications. Thecompositions can be used in the treatment of, for example, fibroids,tumors, internal bleeding, arteriovenous malformations (AVMs), and/orhypervascular tumors. The compositions can be used as, for example,fillers for aneurysm sacs, AAA sac (Type II endoleaks), endoleaksealants, arterial sealants, and/or puncture sealants, and/or can beused to provide occlusion of other lumens such as fallopian tubes.Fibroids can include uterine fibroids which grow within the uterine wall(intramural type), on the outside of the uterus (subserosal type),inside the uterine cavity (submucosal type), between the layers of broadligament supporting the uterus (interligamentous type), attached toanother organ (parasitic type), or on a mushroom-like stalk(pedunculated type). Internal bleeding includes gastrointestinal,urinary, renal and varicose bleeding. AVMs are for example, abnormalcollections of blood vessels, e.g. in the brain, which shunt blood froma high pressure artery to a low pressure vein, resulting in hypoxia andmalnutrition of those regions from which the blood is diverted. In someembodiments, a composition containing the particles can be used toprophylactically treat a condition.

The magnitude of a dose of a composition can vary based on the nature,location and severity of the condition to be treated, as well as theroute of administration. A physician treating the condition, disease ordisorder can determine an effective amount of composition. An effectiveamount of embolic composition refers to the amount sufficient to resultin amelioration of symptoms and/or a prolongation of survival of thesubject, or the amount sufficient to prophylactically treat a subject.The compositions can be administered as pharmaceutically acceptablecompositions to a subject in any therapeutically acceptable dosage,including those administered to a subject intravenously, subcutaneously,percutaneously, intratrachealy, intramuscularly, intramucosaly,intracutaneously, intra-articularly, orally or parenterally.

A composition can include a mixture of particles (e.g., particles thatinclude different types of block copolymers, particles that includedifferent types of therapeutic agents), or can include particles thatare all of the same type. In some embodiments, a composition can beprepared with a calibrated concentration of particles for ease ofdelivery by a physician. A physician can select a composition of aparticular concentration based on, for example, the type of procedure tobe performed. In certain embodiments, a physician can use a compositionwith a relatively high concentration of particles during one part of anembolization procedure, and a composition with a relatively lowconcentration of particles during another part of the embolizationprocedure.

Suspensions of particles in saline solution can be prepared to remainstable (e.g., to remain suspended in solution and not settle and/orfloat) over a desired period of time. A suspension of particles can bestable, for example, for from about one minute to about 20 minutes (e.g.from about one minute to about 10 minutes, from about two minutes toabout seven minutes, from about three minutes to about six minutes).

In some embodiments, particles can be suspended in a physiologicalsolution by matching the density of the solution to the density of theparticles. In certain embodiments, the particles and/or thephysiological solution can have a density of from about one gram percubic centimeter to about 1.5 grams per cubic centimeter (e.g., fromabout 1.2 grams per cubic centimeter to about 1.4 grams per cubiccentimeter, from about 1.2 grams per cubic centimeter to about 1.3 gramsper cubic centimeter).

In some embodiments, the carrier fluid of a composition can include asurfactant. The surfactant can help the particles to mix evenly in thecarrier fluid and/or can decrease the likelihood of the occlusion of adelivery device (e.g., a catheter) by the particles. In certainembodiments, the surfactant can enhance delivery of the composition(e.g., by enhancing the wetting properties of the particles andfacilitating the passage of the particles through a delivery device). Insome embodiments, the surfactant can decrease the occurrence of airentrapment by the particles in a composition (e.g., by porous particlesin a composition). Examples of liquid surfactants include Tween® 80(available from Sigma-Aldrich) and Cremophor EL® (available fromSigma-Aldrich). An example of a powder surfactant is Pluronic® F127 NF(available from BASF). In certain embodiments, a composition can includefrom about 0.05 percent by weight to about one percent by weight (e.g.,about 0.1 percent by weight, about 0.5 percent by weight) of asurfactant. A surfactant can be added to the carrier fluid prior tomixing with the particles and/or can be added to the particles prior tomixing with the carrier fluid.

In some embodiments, among the particles delivered to a subject (e.g.,in a composition), the majority (e.g., about 50 percent or more, about60 percent or more, about 70 percent or more, about 80 percent or more,about 90 percent or more) of the particles can have a diameter of about3,000 microns or less (e.g., about 2,500 microns or less; about 2,000microns or less; about 1,500 microns or less; about 1,200 microns orless; about 1,150 microns or less; about 1,100 microns or less; about1,090 microns or less; about 1,080 microns or less; about 1,070 micronsor less; about 1,060 microns or less; about 1,050 microns or less; about1,040 microns or less; about 1,030 microns or less; about 1,020 micronsor less; about 1,010 microns or less; about 1,000 microns or less; about900 microns or less; about 700 microns or less; about 500 microns orless; about 400 microns or less; about 300 microns or less; about 100microns or less; about 50 microns or less; about 10 microns or less;about five microns or less) and/or about one micron or more (e.g., aboutfive microns or more; about 10 microns or more; about 50 microns ormore; about 100 microns or more; about 300 microns or more; about 400microns or more; about 500 microns or more; about 700 microns or more;about 900 microns or more; about 1,000 microns or more; about 1,010microns or more; about 1,020 microns or more; about 1,030 microns ormore; about 1,040 microns or more; about 1,050 microns or more; about1,060 microns or more; about 1,070 microns or more; about 1,080 micronsor more; about 1,090 microns or more; about 1,100 microns or more; about1,150 microns or more; about 1,200 microns or more; about 1,500 micronsor more; about 2,000 microns or more; about 2,500 microns or more). Insome embodiments, among the particles delivered to a subject, themajority of the particles can have a diameter of less than about 100microns (e.g., less than about 50 microns).

In certain embodiments, the particles delivered to a subject (e.g., in acomposition) can have an arithmetic mean diameter of about 3,000 micronsor less (e.g., about 2,500 microns or less; about 2,000 microns or less;about 1,500 microns or less; about 1,200 microns or less; about 1,150microns or less; about 1,100 microns or less; about 1,090 microns orless; about 1,080 microns or less; about 1,070 microns or less; about1,060 microns or less; about 1,050 microns or less; about 1,040 micronsor less; about 1,030 microns or less; about 1,020 microns or less; about1,010 microns or less; about 1,000 microns or less; about 900 microns orless; about 700 microns or less; about 500 microns or less; about 400microns or less; about 300 microns or less; about 100 microns or less;about 50 microns or less; about 10 microns or less; about five micronsor less) and/or about one micron or more (e.g., about five microns ormore; about 10 microns or more; about 50 microns or more; about 100microns or more; about 300 microns or more; about 400 microns or more;about 500 microns or more; about 700 microns or more; about 900 micronsor more; about 1,000 microns or more; about 1,010 microns or more; about1,020 microns or more; about. 1,030 microns or more; about 1,040 micronsor more; about 1,050 microns or more; about 1,060 microns or more; about1,070 microns or more; about 1,080 microns or more; about 1,090 micronsor more; about 1,100 microns or more; about 1,150 microns or more; about1,200 microns or more; about 1,500 microns or more; about 2,000 micronsor more; about 2,500 microns or more). In some embodiments, theparticles delivered to a subject can have an arithmetic mean diameter ofless than about 100 microns (e.g., less than about 50 microns).

Exemplary ranges for the arithmetic mean diameter of particles deliveredto a subject include from about 100 microns to about 500 microns; fromabout 100 microns to about 300 microns; from about 300 microns to about500 microns; from about 500 microns to about 700 microns; from about 700microns to about 900 microns; from about 900 microns to about 1,200microns; and from about 1,000 microns to about 1,200 microns. Ingeneral, the particles delivered to a subject (e.g., in a composition)can have an arithmetic mean diameter in approximately the middle of therange of the diameters of the individual particles, and a variance ofabout 20 percent or less (e.g. about 15 percent or less, about 10percent or less).

In some embodiments, the arithmetic mean diameter of the particlesdelivered to a subject (e.g., in a composition) can vary depending uponthe particular condition to be treated. As an example, in embodiments inwhich the particles are used to embolize a liver tumor, the particlesdelivered to the subject can have an arithmetic mean diameter of about500 microns or less (e.g., from about 100 microns to about 300 microns;from about 300 microns to about 500 microns). As another example, inembodiments in which the particles are used to embolize a uterinefibroid, the particles delivered to the subject can have an arithmeticmean diameter of about 1,200 microns or less (e.g., from about 500microns to about 700 microns; from about 700 microns to about 900microns; from about 900 microns to about 1,200 microns). As anadditional example, in embodiments in which the particles are used totreat a neural condition (e.g., a brain tumor) and/or head trauma (e.g.,bleeding in the head), the particles delivered to the subject can havean arithmetic mean diameter of less than about 100 microns (e.g., lessthan about 50 microns). As a further example, in embodiments in whichthe particles are used to treat a lung condition, the particlesdelivered to the subject can have an arithmetic mean diameter of lessthan about 100 microns (e.g., less than about 50 microns). As anotherexample, in embodiments in which the particles are used to treat thyroidcancer, the particles can have a diameter of about 1,200 microns or less(e.g., from about 1,000 microns to about 1,200 microns).

The arithmetic mean diameter of a group of particles can be determinedusing a Beckman Coulter RapidVUE Image Analyzer version 2.06 (BeckmanCoulter, Miami, Fla.), described above. The arithmetic mean diameter ofa group of particles (e.g., in a composition) can be determined bydividing the sum of the diameters of all of the particles in the groupby the number of particles in the group.

In certain embodiments, a particle that includes one of theabove-described block copolymers can also include a coating. Forexample, FIG. 4 shows a particle 200 with an interior region 202including a block copolymer matrix 203 and pores 204, and a coating 205formed of a polymer (e.g., polyvinyl alcohol) that is different from theblock copolymer in matrix 203. Coating 205 can, for example, regulatethe release of therapeutic agent from particle 200, and/or can provideprotection to interior region 202 of particle 200 (e.g., during deliveryof particle 200 to a target site). In certain embodiments, coating 205can be formed of a bioerodible and/or bioabsorbable material that canerode and/or be absorbed as particle 200 is delivered to a target site.This can, for example, allow interior region 202 to deliver atherapeutic agent to the target site once particle 200 has reached thetarget site. A bioerodible material can be, for example, apolysaccharide (e.g., alginate); a polysaccharide derivative; aninorganic, ionic salt; a water soluble polymer (e.g., polyvinyl alcohol,such as polyvinyl alcohol that has not been cross-linked); biodegradablepoly DL-lactide-poly ethylene glycol (PELA); a hydrogel (e.g.,polyacrylic acid, hyaluronic acid, gelatin, carboxymethyl cellulose); apolyethylene glycol (PEG); chitosan; a polyester (e.g., apolycaprolactone); a poly(ortho ester); a polyanhydride; apoly(lactic-co-glycolic) acid (e.g., a poly(d-lactic-co-glycolic) acid);a poly(lactic acid) (PLA); a poly(glycolic acid) (PGA); or a combinationthereof In some embodiments, coating 205 can be formed of a swellablematerial, such as a hydrogel (e.g., polyacrylamide co-acrylic acid). Theswellable material can be made to swell by, for example, changes in pH,temperature, and/or salt. In certain embodiments in which particle 200is used in an embolization procedure, coating 205 can swell at a targetsite, thereby enhancing occlusion of the target site by particle 200.

In some embodiments, a particle can include a porous coating that isformed of a block copolymer. For example, FIG. 5 shows a particle 300including an interior region 302 formed of a polymer (e.g., polyvinylalcohol) and a coating 304 formed of a block copolymer (e.g., SIBS)matrix 306. Coating 304 includes pores 308. In certain embodiments,interior region 302 can be formed of a swellable material. Pores 308 incoating 304 can expose interior region 302 to changes in, for example,pH, temperature, and/or salt. When interior region 302 is exposed tothese changes, the swellable material in interior region 302 can swell,thereby causing particle 300 to become enlarged. In certain embodiments,coating 304 can be made of a relatively flexible material (e.g., SIBS)that can accommodate the swelling of interior region 302. Theenlargement of particle 300 can, for example, enhance occlusion duringan embolization procedure.

Examples of swellable materials include hydrogels, such as polyacrylicacid, polyacrylamide co-acrylic acid, hyaluronic acid, gelatin,carboxymethyl cellulose, poly(ethylene oxide)-based polyurethane,polyaspartahydrazide, ethyleneglycoldiglycidylether (EGDGE), andpolyvinyl alcohol (PVA) hydrogels. In some embodiments in which aparticle includes a hydrogel, the hydrogel can be crosslinked, such thatit may not dissolve when it swells. In other embodiments, the hydrogelmay not be crosslinked, such that the hydrogel may dissolve when itswells.

In certain embodiments, a particle can include a coating that includesone or more therapeutic agents. In some embodiments, a particle can havea coating that includes a high concentration of one or more therapeuticagents. One or more of the therapeutic agents can also be loaded intothe interior region of the particle. Thus, the surface of the particlecan release an initial dosage of therapeutic agent, after which the bodyof the particle can provide a burst release of therapeutic agent. Thetherapeutic agent on the surface of the particle can be the same as ordifferent from the therapeutic agent in the body of the particle. Thetherapeutic agent on the surface can be applied by exposing the particleto a high concentration solution of the therapeutic agent.

In some embodiments, a therapeutic agent coated particle can includeanother coating over the surface the therapeutic agent (e.g., abioerodible polymer which erodes when the particle is administered). Thecoating can assist in controlling the rate at which therapeutic agent isreleased from the particle. For example, the coating can be in the formof a porous membrane. The coating can delay an initial burst oftherapeutic agent release. The coating can be applied by dipping orspraying the particle. The bioerodible polymer can be a polysaccharide(such as an alginate). In some embodiments, the coating can be aninorganic, ionic salt. Other bioerodible coatings include polysaccharidederivatives, water-soluble polymers (such as polyvinyl alcohol, e.g.,that has not been cross-linked), biodegradable poly DL-lactide-polyethylene glycol (PELA), hydrogels (e.g., polyacrylic acid, hyaluronicacid, gelatin, carboxymethyl cellulose), polyethylene glycols (PEG),chitosan, polyesters (e.g., polycaprolactones), poly(ortho esters),polyanhydrides, poly(lactic acids) (PLA), polyglycolic acids (PGA),poly(lactic-co-glycolic) acids (e.g., poly(d-lactic-co-glycolic) acids),and combinations thereof. The coating can include therapeutic agent orcan be substantially free of therapeutic agent. The therapeutic agent inthe coating can be the same as or different from an agent on a surfacelayer of the particle and/or within the particle. A polymer coating(e.g., a bioerodible coating) can be applied to the particle surface inembodiments in which a high concentration of therapeutic agent has notbeen applied to the particle surface. Coatings are described, forexample, in DiMatteo et al., U.S. Patent Application Publication No. US2004/0076582 A1, published on Apr. 22, 2004, and entitled “AgentDelivery Particle”, which is incorporated herein by reference.

In some embodiments, a particle can include one or more smallersub-particles. For example, FIG. 6 shows a particle 400 that includes amatrix 402 and pores 406 within matrix 402. Particle 400 also includessub-particles 404 that are embedded within matrix 402. Matrix 402 can beformed of, for example, one or more polymers (e.g., block copolymerssuch as SIBS). Alternatively or additionally, sub-particles 404 can beformed of one or more polymers (e.g., block copolymers such as SIBS). Insome embodiments, both matrix 402 and sub-particles 404 can be formed ofone or more block copolymers. Block copolymer(s) in matrix 402 can bethe same as, or different from, block copolymer(s) in sub-particles 404.In certain embodiments, particle 400 can include one or more therapeuticagents, such as water-soluble therapeutic agents and/or organic-solubletherapeutic agents. This can allow particle 400 to be used, for example,to deliver multiple therapeutic agents to a target site in oneprocedure. The therapeutic agents can be included in (e.g., dispersedthroughout) matrix 402 and/or sub-particles 404. In some embodiments,matrix 402 can include one type of therapeutic agent (e.g., anorganic-soluble therapeutic agent), while sub-particles 404 includeanother type of therapeutic agent (e.g., a water-soluble therapeuticagent). In certain embodiments, matrix 402 can be made out of a porousmaterial (e.g., SIBS), which can help in the release of therapeuticagent from sub-particles 404. Examples of water-soluble therapeuticagents include DNA, oligonucleotides, heparin, urokinase, halofuginone,and protein. Examples of organic-soluble therapeutic agents includepaclitaxel, trans-retinoic acid, mithramycin, probucol, rapamycin,dexamethason, 5-fluorouracil, methotrexate, doxorubicin, daunorubicin,cyclosporine, cisplatin, vinblastine, vincristine, colchicine,epothilones, endostatin, angiostatin, and plicamycin.

Particles can be formed by any of a number of different methods. As anexample, FIGS. 7A-7C show a single-emulsion process that can be used,for example, to make particle 100 (FIGS. 1A and 1B). As shown in FIGS.7A-7C, a drop generator 500 (e.g., a pipette) forms drops 510 of asolution including a block copolymer (e.g., SIBS) and an organic solvent(e.g., methylene chloride, chloroform, tetrahydrofuran (THF), toluene).In some embodiments, the solution can include at least about one percentweight/volume (w/v) (e.g., from about one percent w/v to about 20percent w/v) of the block copolymer. Drops 510 fall from drop generator500 into a vessel 520 that contains an aqueous solution including asurfactant. In some embodiments, the surfactant can be water-soluble.Examples of surfactants include polyvinyl alcohols, poly(vinylpyrrolidone) (PVP), and polysorbates (e.g., Tween® 20, Tween® 80). Incertain embodiments, the aqueous solution can be mixed (e.g.,homogenized) while drops 510 are being added to it. In some embodiments,the aqueous solution can be mixed at a speed of at most about 10,000revolutions per minute (e.g., at most about 5,000 revolutions perminute, at most about 1,500 revolutions per minute). The concentrationof the surfactant in the aqueous solution can be at least 0.05 percentw/v (e.g., from 0.05 percent w/v to about 10 percent w/v). In general,as the concentration of surfactant in the aqueous solution increases,particle size can decrease.

As FIG. 7B shows, after drops 510 have fallen into vessel 520, thesolution is mixed using a stirrer 530. In some embodiments, the solutioncan be mixed (e.g., homogenized) at a speed of at least about 1,000revolutions per minute (e.g., at least about 2,500 revolutions perminute, at least about 5,000 revolutions per minute, at least about6,000 revolutions per minute, at least about 7,500 revolutions perminute) and/or at most about 10,000 revolutions per minute (e.g., atmost about 7,500 revolutions per minute, at most about 6,000 revolutionsper minute, at most about 5,000 revolutions per minute, at most about2,500 revolutions per minute). For example, the solution can be mixed ata speed of from about 1000 revolutions per minute to about 6000revolutions per minute. In certain embodiments, as mixing (e.g.,homogenization) speed increases, particle size can decrease. In someembodiments, the solution can be mixed for a period of at least about0.5 hour (e.g., at least about one hour, at least about two hours, atleast about three hours, at least about four hours) and/or at most aboutfive hours (e.g., at most about four hours, at most about three hours,at most about two hours, at most about one hour). In certainembodiments, the solution can be mixed for a period of from about onehour to about three hours (e.g., for about one hour). In someembodiments, mixing can occur at a temperature of at least about 25° C.(e.g., at least about 30° C., at least about 35° C.). In general, asmixing (e.g., homogenization) temperature increases, particle size canincrease. The mixing results in a suspension 540 that includes particles100 suspended in the solvent (FIG. 7C). Particles 100 are then separatedfrom the solvent by, for example, filtration, or centrifuging followedby removal of the supernatant. Thereafter, particles 100 are dried(e.g., by evaporation, by lyophilization, by vacuum drying).

In some embodiments, certain materials and/or methods can be used duringa particle formation process, such as the above-describedsingle-emulsion process, to promote the formation of pores 104.

As an example, in certain embodiments, pores 104 can be formed by addingat least one salt into the solution that is used to form drops 510.Examples of salts include sodium chloride, calcium chloride, and sodiumbicarbonate. In some embodiments, the salt can be kosher salt and/or seasalt. In certain embodiments, the salt can be in the form of particles.One or more of the salt particles can have a maximum dimension of atleast 0.01 micron (e.g., at least 0.05 micron, at least about 0.1micron, at least about 0.5 micron, at least about one micron, at leastabout five microns, at least about 10 microns, at least about 15microns, at least about 20 microns, at least about 25 microns, at leastabout 30 microns, at least about 35 microns, at least about 50 microns,at least about 100 microns, at least about 150 microns, at least about200 microns, at least about 250 microns), and/or at most about 300microns (e.g., at most about 250 microns, at most about 200 microns, atmost about 150 microns, at most about 100 microns, at most about 50microns, at most about 35 microns, at most about 30 microns, at mostabout 25 microns, at most about 20 microns, at most about 15 microns, atmost about 10 microns, at most about five microns, at most about onemicron, at most about 0.5 micron, at most about 0.1 micron, at mostabout 0.05 micron).

Particles formed from drops 510 when drops 510 include one or more saltscan include the salts incorporated into a block copolymer matrix. Toremove the salts from the particles, the particles can be contacted withwater. For example, the particles can be placed in a water bath. In someembodiments, the water bath can have a temperature of at least about 20°C. (e.g., at least about 25° C., at least about 30° C.). The water inthe water bath can dissolve the salt within the particles, therebyforming pores 104. In certain embodiments, after the particles have beenformed, they can remain in vessel 520 for a period of time, therebyallowing the aqueous solution in vessel 520 to dissolve the salt in theparticles and form pores 104.

In some embodiments, salt particles of different sizes can be used toform pores of different sizes. For example, in certain embodiments, someof the salt particles can have a maximum dimension of from 0.01 micronto about one micron, and some of the salt particles can have a maximumdimension of from about 10 microns to about 300 microns. In someembodiments, the dimensions of the salt particles can be selected toaccount for a predicted extent of premature salt dissolution (e.g.,during the single-emulsion process). For example, in some embodiments, asalt particle that is used to form a pore can have a maximum dimensionthat is at least about two times larger, and/or at most about 10 timeslarger, than a corresponding maximum dimension of the pore.

As another example, in certain embodiments, pores 104 can be formed byadding at least one water-soluble polymer into the solution that is usedto form drops 510. Examples of water-soluble polymers includepolyethylene glycol, polyvinylpyrrolidone, carboxymethylcellulose, andhydroxyethylcellulose. Particles formed from drops 510 when drops 510include one or more water-soluble polymers can include the water-solublepolymers incorporated into a block copolymer matrix. To remove thewater-soluble polymers from the particles, the particles can becontacted with water (e.g., as described above). The water can dissolvethe water-soluble polymers within the particles, thereby forming pores104. In some embodiments, the amount of water-soluble polymer includedin the solution that is used to form drops 510 can be selected toaccount for premature dissolution of some of the water-soluble polymer(e.g., during the single-emulsion process).

As an additional example, in some embodiments, pores 104 can be formedby adding at least one base into the solution that is used to form drops510. Examples of bases include sodium bicarbonate, ammonium bicarbonate,and potassium bicarbonate. In certain embodiments, the base can be inthe form of particles. One or more of the particles can have a maximumdimension of at least 0.01 micron (e.g., at least about 0.05 micron, atleast about 0.1 micron, at least about 0.5 micron, at least about onemicron, at least about five microns, at least about 10 microns, at leastabout 15 microns, at least about 20 microns, at least about 25 microns,at least about 30 microns, at least about 35 microns, at least about 50microns, at least about 100 microns, at least about 150 microns, atleast about 200 microns, at least about 250 microns), and/or at mostabout 300 microns (e.g., at most about 250 microns, at most about 200microns, at most about 150 microns, at most about 100 microns, at mostabout 50 microns, at most about 35 microns, at most about 30 microns, atmost about 25 microns, at most about 20 microns, at most about 15microns, at most about 10 microns, at most about five microns, at mostabout one micron, at most about 0.5 micron, at most about 0.1 micron, atmost about 0.05 micron).

In some embodiments, pores 104 can be formed by reacting the base withan acid. For example, in certain embodiments, the aqueous solution invessel 520 can include at least one acid. Examples of acids includecitric acid, acetic acid, and hydrochloric acid. When drops 510 contactthe acid in the aqueous solution in vessel 520, the base in drops 510can react with the acid, generating at least one gas (e.g., carbondioxide and/or ammonia). For example, in some embodiments, drops 510 caninclude sodium bicarbonate and the aqueous solution in vessel 520 caninclude citric acid. When drops 510 contact the aqueous solution invessel 520, the sodium bicarbonate in drops 510 can react with thecitric acid in the aqueous solution, thereby generating carbon dioxidegas. The generation of the gas during the formation of particles 100 canresult in the generation of pores 104.

In certain embodiments, vessel 520 can be heated and/or can bemaintained in an atmosphere having a relatively low pressure. This can,for example, cause the salt (e.g., ammonium bicarbonate) in drops 510 tosublimate, thereby producing a gas that can result in the formation ofpores 104. In some embodiments, vessel 520 can be heated to atemperature of at least about 70° C. (e.g., at least about 80° C., atleast about 90° C.). The temperature of vessel 520 can be increased by,for example, placing vessel 520 in a hot water bath, placing a waterjacket around vessel 520 and flowing hot water through the water jacket,and/or heating vessel 520 on a hot plate. In certain embodiments, vessel520 can be maintained in an atmosphere having a pressure of less than 30inches Hg (e.g., at most about 25 inches Hg, at most about 20 inches Hg,at most about 15 inches Hg, at most about 10 inches Hg, at most aboutfive inches Hg). For example, vessel 520 can be situated in a sealedchamber that is connected to a vacuum pump. The vacuum pump can be usedto maintain a relatively low pressure within the chamber. An example ofa vacuum pump is the Adixen ACP 15 series dry roughing pump (fromAlcatel Vacuum Products, Hingham, Mass.).

As a further example, in some embodiments, pores 104 can be formed usinga solvent evaporation process. For example, during the single-emulsionprocess described with reference to FIGS. 7A-7C, the solvent in drops510 can be evaporated at an accelerated rate. In certain embodiments,this accelerated evaporation of the solvent can result in the formationof pores 104. Without wishing to be bound by theory, it is believed thataccelerating the solvent evaporation rate during the particle formationprocess can result in incomplete annealing and ordering of the blockcopolymer. The result can be the formation of a block copolymer matrixincluding pores.

In certain embodiments, the evaporation rate of the solvent can beincreased by increasing the temperature of the single-emulsion process.For example, in some embodiments, the single-emulsion process can takeplace at a temperature of at least about 40° C. In certain embodiments(e.g., in certain embodiments in which the solvent in vessel 520 istoluene), the single-emulsion process can take place at a temperature ofabout 70° C. In some embodiments (e.g., some embodiments in which thesolvent in vessel 520 is chloroform), the single-emulsion process cantake place at a temperature of about 60° C.

In certain embodiments, the single-emulsion process can take place at atemperature of at most about 90° C. In some embodiments, maintaining thesingle-emulsion process at a temperature of at most about 90° C. canincrease the likelihood of particle formation.

In certain embodiments, the evaporation rate of the solvent can beincreased by decreasing the pressure of the atmosphere in which thesingle-emulsion process takes place. The atmosphere of thesingle-emulsion process can be maintained at a relatively low pressureby, for example, conducting the single-emulsion process in a sealedchamber that is connected to a vacuum pump. In some embodiments, thesingle-emulsion process can take place in at atmosphere having apressure of less than 30 inches Hg (e.g., at most about 25 inches Hg, atmost about 20 inches Hg, at most about 15 inches Hg, at most about 10inches Hg, at most about five inches Hg).

In certain embodiments, one or more combinations of the above-describedmethods can be used to form pores 104.

In certain embodiments, after particle 100 has been formed, one or moretherapeutic agents can be incorporated into particle 100. Thetherapeutic agents can be incorporated into particle 100 by, forexample, immersing particle 100 in the therapeutic agents (e.g., in asolution including the therapeutic agents), and/or spraying particle 100with the therapeutic agents (e.g., with a solution including thetherapeutic agents). The porosity of particle 100 can, for example, helpthe therapeutic agents to diffuse into particle 100 and/or can helpparticle 100 to retain a relatively high volume of the therapeuticagents.

In certain embodiments, after one or more therapeutic agents have beenadded to particle 100, particle 100 can be dried (e.g., lyophilized).This drying of particle 100 can, for example, result in drying of thetherapeutic agent in particle 100 as well. In some embodiments, particle100 may be able to retain a dried therapeutic agent relatively easily(e.g., prior to use, such as during storage).

In some embodiments, one or more therapeutic agents can be included inthe process described with reference to FIGS. 7A-7C. In certainembodiments, this can result in the formation of particles that includethe therapeutic agents. For example, in some embodiments, drops 510 canbe formed of a solution including a block copolymer, an organic solvent,and a therapeutic agent. In certain embodiments, particle 100 caninclude the therapeutic agent when particle 100 is formed.

In some embodiments, particles that are formed using the above-describedprocess can be coated (e.g., with a polymer). The coating can be addedto the particles by, for example, spraying and/or dip-coating. Thesecoating processes can be used, for example, to make particles likeparticle 200 (FIG. 4).

While a pipette has been described as an example of a drop generatorthat can be used in a particle formation process, in some embodiments,other types of drop generators or drop generator systems can be used ina particle formation process. For example, FIG. 8 shows a drop generatorsystem 601 that includes a flow controller 600, a viscosity controller605, a drop generator 610, and a vessel 620. Flow controller 600delivers a solution (e.g., a solution that contains a block copolymersuch as SIBS, a therapeutic agent, and an organic solvent) to aviscosity controller 605, which heats the solution to reduce viscosityprior to delivery to drop generator 610. The solution passes through anorifice in a nozzle in drop generator 610, forming drops of thesolution. The drops are then directed into vessel 620 (e.g., containingan aqueous solution that includes a surfactant such as PVA). Dropgenerators are described, for example, in Lanphere et al., U.S. PatentApplication Publication No. US 2004/0096662 A1, published on May 20,2004, and entitled “Embolization”, and in DiCarlo et al., U.S. patentapplication Ser. No. 11/111,511, filed on Apr. 21, 2005, and entitled“Particles”, both of which are incorporated herein by reference.

FIGS. 9A and 9B show an embodiment of a system 602 that includes dropgenerator system 601, and that can be used to make particles likeparticle 200 (FIG. 4) and particle 300 (FIG. 5). System 602 includes adrop generator system 601, a reactor vessel 630, a gel dissolutionchamber 640 and a filter 650. As shown in FIG. 9B, flow controller 600delivers a solution that contains one or more polymers (e.g., a blockcopolymer) and a gelling precursor (e.g., alginate) to viscositycontroller 605, which heats the solution to reduce viscosity prior todelivery to drop generator 610. The solution passes through an orificein a nozzle in drop generator 610, forming drops of the solution. Thedrops are then directed into vessel 620 (in this process, used as agelling vessel), where the drops contact a gelling agent (e.g., calciumchloride) that converts the gelling precursor from a solution form intoa gel form, stabilizing the drops and forming particles. In someembodiments, the particles may be transferred from vessel 620 to reactorvessel 630, where one or more polymers in the gel-stabilized particlesmay be reacted (e.g., cross-linked). In certain embodiments, theparticles may be transferred to gel dissolution chamber 640, where thegelling precursor (which was converted to a gel) can be removed from theparticles. In some embodiments, the removal of the gel from theparticles can result in the formation of pores in the particles. Afterthey have been formed, the particles can be filtered in filter 650 toremove debris. In some embodiments, the particles may thereafter becoated with, for example, a polymer (e.g., a polyvinyl alcohol).Finally, the particles can be sterilized and packaged as, for example,an embolic composition including the particles.

While alginate has been described as a gelling precursor, other types ofgelling precursors can be used. Gelling precursors include, for example,alginate salts, xanthan gums, natural gum, agar, agarose, chitosan,carrageenan, fucoidan, furcellaran, laminaran, hypnea, eucheuma, gumarabic, gum ghatti, gum karaya, gum tragacanth, hyaluronic acid, locustbeam gum, arabinogalactan, pectin, amylopectin, other water solublepolysaccharides and other ionically cross-linkable polymers. Aparticular gelling precursor is sodium alginate, such as high guluronicacid, stem-derived alginate (e.g., about 50 percent or more, about 60percent or more guluronic acid) with a low viscosity (e.g., from about20 centipoise to about 80 centipoise at 20° C.), which can produce ahigh tensile, robust gel.

As described above, in some embodiments (e.g., embodiments in whichalginate is used as a gelling precursor), vessel 620 can include agelling agent such as calcium chloride. The calcium cations in thecalcium chloride have an affinity for carboxylic groups in the gellingprecursor. In some embodiments, the cations complex with carboxylicgroups in the gelling precursor. Without wishing to be bound by theory,it is believed that the complexing of the cations with carboxylic groupsin the gelling precursor can cause different regions of the gellingprecursor to be pulled closer together, causing the gelling precursor togel. In certain embodiments, the complexing of the cations withcarboxylic groups in the gelling precursor can result in encapsulationof one or more other polymers (e.g., a block copolymer) in a matrix ofgelling precursor.

While calcium chloride has been described as a gelling agent, othertypes of gelling agents can be used. Examples of gelling agents includedivalent cations such as alkali metal salts, alkaline earth metal salts,or transition metal salts that can jonically cross-link with the gellingprecursor. In some embodiments, an inorganic salt, such as a calcium,barium, zinc or magnesium salt, can be used as a gelling agent.

Examples of cross-linking agents that may be used to react one or moreof the polymers (e.g., polyvinyl alcohol) in reactor vessel 630 includeone or more aldehydes (e.g., formaldehyde, glyoxal, benzaldehyde,aterephthalaldehyde, succinaldehyde, glutaraldehyde) in combination withone or more acids, such as relatively strong acids (e.g., sulfuric acid,hydrochloric acid, nitric acid) and/or relatively weak acids (e.g.,acetic acid, formic acid, phosphoric acid).

In certain embodiments, it can be desirable to reduce the surfacetension of the mixture contained in vessel 620 (e.g., when formingparticles having a diameter of about 500 microns or less). This can beachieved, for example, by heating the mixture in vessel 620 (e.g., to atemperature greater than room temperature, such as a temperature ofabout 30° C. or more), by bubbling a gas (e.g., air, nitrogen, argon,krypton, helium, neon) through the mixture contained in vessel 620, bystirring (e.g., via a magnetic stirrer) the mixture contained in vessel620, by including a surfactant in the mixture containing the gellingagent, and/or by forming a mist containing the gelling agent above themixture contained in vessel 620 (e.g., to reduce the formation of tailsand/or enhance the sphericity of the particles).

In certain embodiments, particles can be formed by omitting one or moreof the steps from the process described with reference to FIGS. 9A and9B. For example, one or more of the polymers may not be crosslinked,and/or the gelling precursor may not be removed.

In some embodiments, particles can be formed using a double-emulsionprocess. For example, FIGS. 10A-10F show a double-emulsion process thatcan be used to make particles that, like particle 400 (FIG. 6), includesub-particles.

First, drop generator 800 (e.g., a pipette) forms drops 810 of anaqueous solution containing a water-soluble therapeutic agent (e.g.,DNA) and a surfactant. In some embodiments, the surfactant can bewater-soluble. Examples of surfactants include polyvinyl alcohols,poly(vinyl pyrrolidone) (PVP), and polysorbates (e.g., Tween® 20, Tween®80). Drops 810 fall into a vessel 820 that includes a solution of ablock copolymer (e.g., SIBS) and an organic-soluble therapeutic agent(e.g., paclitaxel) dissolved in an organic solvent, forming a mixture830. As shown in FIG. 10B, mixture 830 is then mixed (e.g., homogenized)using a stirrer 835, to produce a suspension 832 that includessub-particles 404 suspended in solvent (FIG. 10C). Mixing of mixture 830can occur at a speed of, for example, at least about 5,000 revolutionsper minute (e.g., at least about 7,500 revolutions per minute) and/or atmost about 10,000 revolutions per minute (e.g., at most about 7,500revolutions per minute). In some embodiments, mixture 830 can be mixedfor a period of at least about one minute (e.g., at least about twominutes, at least about five minutes, at least about seven minutes)and/or at most about 10 minutes (e.g., at most about seven minutes, atmost about five minutes, at most about two minutes). For example,mixture 830 may be mixed for a period of from about one minute to aboutfive minutes.

After suspension 832 has been formed, suspension 832 is added to a dropgenerator 840 (FIG. 10D) to produce drops 850. Drops 850 fall into avessel 870 that includes an aqueous solution, forming a mixture 880. Insome embodiments, the aqueous solution in vessel 870 includes asurfactant (e.g., PVA). As FIG. 10E shows, mixture 880 is mixed (e.g.,homogenized) using a stirrer 885, at a mixing speed that is lower thanthe speed of the first mixing. In certain embodiments, mixture 880 canbe mixed at a speed of at most about 2,000 revolutions per minute (e.g.,at most about 1,500 revolutions per minute, at most about 1,000revolutions per minute, at most about 500 revolutions per minute) and/orat least about 100 revolutions per minute (e.g., at least about 500revolutions per minute, at least about 1,000 revolutions per minute, atleast about 1,500 revolutions per minute). This second mixing can lastfor a period of, for example, at least about one minute (e.g., at leastabout two minutes, at least about four minutes, at least about sixminutes, at least about eight minutes, at least about 10 minutes, atleast about 20 minutes, at least about 30 minutes, at least about 40minutes, at least about 50 minutes, at least about one hour, at leastabout two hours, at least about four hours, at least about six hours, atleast about eight hours, at least about 10 hours) and/or at most about12 hours (e.g., at most about 10 hours, at most about 8 hours, at mostabout 6 hours, at most about four hours, at most about two hours, atmost about one hour, at most about 50 minutes, at most about 40 minutes,at most about 30 minutes, at most about 20 minutes, at most about 10minutes, at most about eight minutes, at most about six minutes, at mostabout four minutes, at most about two minutes). Mixing (e.g.,homogenization) of mixture 880 produces a suspension 890 includingparticles 400 in solvent (FIG. 10F). Particles 400 are then separatedfrom the solvent (e.g., by filtration) and dried (e.g., by evaporation).In some embodiments, particles 400 are separated from the solvent byevaporating the solvent.

In certain embodiments, one or more of the therapeutic agents can beomitted from the above-described process. In some embodiments, all ofthe therapeutic agents can be omitted from the above-described process,such that the particles that are produced do not include any therapeuticagent. Alternatively or additionally, one or more therapeutic agents canbe added to the particles (e.g., by absorption) after the particles havebeen formed.

In some embodiments, certain materials and/or methods can be used duringthe double-emulsion process to promote the formation of pores inparticles formed by the double-emulsion process. For example, in certainembodiments, the double-emulsion process can take place at a temperatureof at least about 40° C. (e.g., at least about 50° C., at least about60° C.), and/or in an atmosphere having a pressure of less than 30inches Hg (e.g., at most about 25 inches Hg, at most about 20 inches Hg,at most about 15 inches Hg, at most about 10 inches Hg, at most aboutfive inches Hg) (e.g., as described above with respect to thesingle-emulsion process). In some embodiments, one or more salts, bases,and/or water-soluble polymers can be combined with the organic solventand used to form porous particles (e.g., as described above with respectto the single-emulsion process).

Methods of forming particles are described in, for example, Song et al.,U.S. patent application Ser. No. 11/314,056, filed on Dec. 21, 2005 andentitled “Block Copolymer Particles”; Song et al., U.S. patentapplication Ser. No. 11/314,557, filed on Dec. 21, 2005 and entitled“Block Copolymer Particles”; Buiser et al., U.S. Patent ApplicationPublication No. US 2003/0185896 A1, published on Oct. 2, 2003, andentitled “Embolization”; Lanphere et al., U.S. Patent ApplicationPublication No. US 2004/0096662 A1, published on May 20, 2004, andentitled “Embolization”; Lanphere et al., U.S. Patent ApplicationPublication No. US 2005/0263916 A1, published on Dec. 1, 2005, andentitled “Embolization”; and DiCarlo et al., U.S. patent applicationSer. No. 11/111,511, filed on Apr. 21, 2005, and entitled “Particles”,all of which are herein incorporated by reference.

OTHER EMBODIMENTS

While certain embodiments have been described, other embodiments arepossible.

As an example, in some embodiments, a particle can include one or morechannels, either in addition to pores, or as an alternative to pores.For example, FIG. 11 shows a particle 900 that is formed of a blockcopolymer matrix 902. Particle 900 includes pores 904 and channels 906.The presence of channels 906 in particle 900 can, for example, helpparticle 900 to absorb and/or retain therapeutic agent, and/or torelease therapeutic agent (e.g., at a target site). In some embodiments,a particle such as particle 900 can be formed using a single-emulsionprocess, such as the single-emulsion process described with reference toFIGS. 7A-7C. In certain embodiments, during a single-emulsion process,the drops that are contacted with an aqueous solution can be formed of asolution including a block copolymer, an organic solvent, and one ormore water-soluble polymers. As the drops are formed into particles,some or all of the water-soluble polymers can leach through thehardening block copolymer, thereby forming channels 906.

As another example, in some embodiments, a particle can encapsulate oneor more therapeutic agents. For example, FIG. 12 shows a particle 950having a shell 952 formed of a block copolymer matrix 953 and includingpores 954. Shell 952 encapsulates a therapeutic agent 956. Particle 950can be formed, for example, by forming a particle out of a bioerodibleand/or bioabsorbable material, forming a porous block copolymer coatingover the particle, eroding and/or absorbing the bioerodible and/orbioabsorbable material, and soaking the resulting shell 952 in asolution including therapeutic agent 956.

As a further example, in some embodiments, multiple salt particlesand/or base particles can agglomerate during a porous particle formationprocess. This agglomeration can result in the formation of a porousparticle including one or more relatively large pores having dimensionsthat are larger than those of the individual salt particles and/or baseparticles.

As an additional example, in certain embodiments a particle can includea block copolymer and a bioabsorbable and/or bioerodible materialdispersed uniformly or non-uniformly throughout the block copolymer. Thebioabsorbable and/or bioerodible material can, for example, help todelay and/or moderate therapeutic agent release from the particle.

As a further example, while particles including sub-particles embeddedwithin a porous matrix have been described, in some embodiments, aparticle can include sub-particles (e.g., porous sub-particles,non-porous sub-particles) embedded within a non-porous matrix. Incertain embodiments, a particle can include porous sub-particlesembedded within a porous matrix.

As another example, in some embodiments in which a particle thatincludes a block copolymer is used for embolization, the particle canalso include one or more other embolic agents, such as a sclerosingagent (e.g., ethanol), a liquid embolic agent (e.g.,n-butyl-cyanoacrylate), and/or a fibrin agent. The other embolicagent(s) can enhance the restriction of blood flow at a target site.

As a further example, in some embodiments a particle does not includeany therapeutic agents.

As another example, in some embodiments a porous particle can have asubstantially uniform pore structure. Alternatively, a porous particlecan have a non-uniform pore structure. For example, the particle canhave a substantially non-porous interior region (e.g., formed of apolyvinyl alcohol) and a porous exterior region (e.g., formed of amixture of a polyvinyl alcohol and alginate). Porous particles aredescribed, for example, in Lanphere et al., U.S. Patent ApplicationPublication No. US 2004/0096662 A1, published on May 20, 2004, andentitled “Embolization”, which is incorporated herein by reference.

As an additional example, in some embodiments, a particle that includesa block copolymer can also include a shape memory material, which iscapable of being configured to remember (e.g., to change to) apredetermined configuration or shape. In certain embodiments, particlesthat include a shape memory material can be selectively transitionedfrom a first state to a second state. For example, a heating deviceprovided in the interior of a delivery catheter can be used to cause aparticle including a shape memory material to transition from a firststate to a second state. Shape memory materials and particles thatinclude shape memory materials are described in, for example, Bell etal., U.S. Patent Application Publication No. US 2004/0091543 A1,published on May 13, 2004, and entitled “Embolic Compositions”, andDiCarlo et al., U.S. Patent Application Publication No. US 2005/0095428A1, published on May 5, 2005, and entitled “Embolic Compositions”, bothof which are incorporated herein by reference.

As another example, in some embodiments, a particle that includes ablock copolymer can also include a surface preferential material.Surface preferential materials are described, for example, in DiCarlo etal., U.S. Patent Application Publication No. US 2005/0196449 A1,published on Sep. 8, 2005, and entitled “Embolization”, which isincorporated herein by reference.

As a further example, while homogenization has been described in thesingle-emulsion and double-emulsion processes that can be used to formparticles (e.g. particles including SIBS), in some embodiments,vortexing or sonication can be used as an alternative to, or in additionto, homogenization.

As another example, in certain embodiments, particles can be linkedtogether to form particle chains. For example, the particles can beconnected to each other by links that are formed of one or more of thesame material(s) as the particles, or of one or more differentmaterial(s) from the particles. Particle chains and methods of makingparticle chains are described, for example, in Buiser et al., U.S.Patent Application Publication No. US 2005/0238870 A1, published on Oct.27, 2005, and entitled “Embolization”, which is incorporated herein byreference.

As an additional example, in some embodiments one or more particlesis/are substantially nonspherical. In some embodiments, particles can bemechanically shaped during or after the particle formation process to benonspherical (e.g., ellipsoidal). In certain embodiments, particles canbe shaped (e.g., molded, compressed, punched, and/or agglomerated withother particles) at different points in the particle manufacturingprocess. As an example, in some embodiments in which particles includeSIBS, the particles can be sufficiently flexible and/or moldable to beshaped. As another example, in certain embodiments in which particlesare formed using a gelling agent, the particles can be physicallydeformed into a specific shape and/or size after the particles have beencontacted with the gelling agent, but before the polymer(s) in theparticles have been cross-linked. After shaping, the polymer(s) (e.g.,polyvinyl alcohol) in the particles can be cross-linked, optionallyfollowed by substantial removal of gelling precursor (e.g., alginate).While substantially spherical particles have been described, in someembodiments, nonspherical particles can be manufactured and formed bycontrolling, for example, drop formation conditions. In someembodiments, nonspherical particles can be formed by post-processing theparticles (e.g., by cutting or dicing into other shapes).

Particle shaping is described, for example, in Baldwin et al., U.S.Patent Application Publication No. US 2003/0203985 A1, published on Oct.30, 2003, and entitled “Forming a Chemically Cross-Linked Particle of aDesired Shape and Diameter”, which is incorporated herein by reference.

As a further example, in some embodiments, particles can be used fortissue bulking. As an example, the particles can be placed (e.g.,injected) into tissue adjacent to a body passageway. The particles cannarrow the passageway, thereby providing bulk and allowing the tissue toconstrict the passageway more easily. The particles can be placed in thetissue according to a number of different methods, for example,percutaneously, laparoscopically, and/or through a catheter. In certainembodiments, a cavity can be formed in the tissue, and the particles canbe placed in the cavity. Particle tissue bulking can be used to treat,for example, intrinsic sphincteric deficiency (ISD), vesicoureteralreflux, gastroesophageal reflux disease (GERD), and/or vocal cordparalysis (e.g., to restore glottic competence in cases of paralyticdysphonia). In some embodiments, particle tissue bulking can be used totreat urinary incontinence and/or fecal incontinence. The particles canbe used as a graft material or a filler to fill and/or to smooth outsoft tissue defects, such as for reconstructive or cosmetic applications(e.g., surgery). Examples of soft tissue defect applications includecleft lips, scars (e.g., depressed scars from chicken pox or acnescars), indentations resulting from liposuction, wrinkles (e.g.,glabella frown wrinkles), and soft tissue augmentation of thin lips.Tissue bulking is described, for example, in Bourne et al., U.S. PatentApplication Publication No. US 2003/0233150 A1, published on Dec. 18,2003, and entitled “Tissue Treatment”, which is incorporated herein byreference.

As an additional example, in some embodiments, particles can be used inan ablation procedure. For example, the particles may include one ormore ferromagnetic materials and may be used to enhance ablation at atarget site. Ablation is described, for example, in Rioux et al., U.S.Patent Application Publication No. US 2004/0101564 A1, published on May27, 2004, and entitled “Embolization”; Lanphere et al. U.S. PatentApplication Publication No. US 2005/0129775 A1, published on Jun. 16,2005, and entitled “Ferromagnetic Particles and Methods”; and Lanphereet al., U.S. patent application Ser. No. 11/117,156, filed on Apr. 28,2005, and entitled “Tissue-Treatment Methods”, all of which areincorporated herein by reference.

As another example, in some embodiments a solution can be added to thenozzle of a drop generator to enhance the porosity of particles producedby the drop generator. Examples of porosity-enhancing solutions includestarch, sodium chloride at a relatively high concentration (e.g., morethan about 0.9 percent, from about one percent to about five percent,from about one percent to about two percent), and calcium chloride(e.g., at a concentration of at least about 50 mM). For example, calciumchloride can be added to a sodium alginate gelling precursor solution toincrease the porosity of the particles produced from the solution.

As a further example, while certain methods of making particles havebeen described, in some embodiments, other methods can be used to makeparticles. For example, in some embodiments (e.g., in some embodimentsin which particles having a diameter of less than about one micron arebeing formed), particles can be formed using rotor/stator technology(e.g., Polytron® rotor/stator technology from Kinmatica Inc.),high-pressure homogenization (e.g., using an APV-Gaulin microfluidizeror Gaulin homogenizer), mechanical shear (e.g., using a Gifford Woodcolloid mill), and/or ultrasonification (e.g., using either a probe or aflow-through cell).

As an additional example, in some embodiments, particles havingdifferent shapes, sizes, physical properties, and/or chemicalproperties, can be used together in an embolization procedure. Thedifferent particles can be delivered into the body of a subject in apredetermined sequence or simultaneously. In certain embodiments,mixtures of different particles can be delivered using a multi-lumencatheter and/or syringe. In some embodiments, particles having differentshapes and/or sizes can be capable of interacting synergistically (e.g.,by engaging or interlocking) to form a well-packed occlusion, therebyenhancing embolization. Particles with different shapes, sizes, physicalproperties, and/or chemical properties, and methods of embolizationusing such particles are described, for example, in Bell et al., U.S.Patent Application Publication No. US 2004/0091543 A1, published on May13, 2004, and entitled “Embolic Compositions”, and in DiCarlo et al.,U.S. Patent Application Publication No. US 2005/0095428 A1, published onMay 5, 2005, and entitled “Embolic Compositions”, both of which areincorporated herein by reference.

Other embodiments are in the claims.

1. A particle comprising a block copolymer and having at least one pore,wherein the particle has a diameter of about 3,000 microns or less. 2.The particle of claim 1, wherein the particle further comprises atherapeutic agent.
 3. The particle of claim 1, wherein the blockcopolymer includes at least one first block having a glass transitiontemperature of at most 37° C. and at least one second block having aglass transition temperature of greater than 37° C.
 4. The particle ofclaim 3, wherein the at least one first block comprises at least onepolyolefin block.
 5. The particle of claim 3, wherein the at least onefirst block comprises at least one isobutylene monomer.
 6. The particleof claim 3, wherein the at least one second block comprises at least oneblock selected from the group consisting of vinyl aromatic blocks,methacrylate blocks, and combinations thereof.
 7. The particle of claim3, wherein the at least one first block comprises at least oneisobutylene monomer and the at least one second block comprises at leastone monomer selected from the group consisting of styrene,α-methylstyrene, and combinations thereof.
 8. The particle of claim 1,wherein the block copolymer has the formula X-(AB)_(n), A is apolyolefin block, B is a vinyl aromatic block or a methacrylate block, nis a positive whole number, and X is an initiator.
 9. The particle ofclaim 1, wherein the block copolymer has the formula BAB or ABA, inwhich A is a first block and B is a second block.
 10. The particle ofclaim 1, wherein the block copolymer has the formula B(AB)_(n) orA(BA)_(n), in which A is a first block, B is a second block, and n is apositive whole number.
 11. The particle of claim 1, wherein the blockcopolymer forms a coating on the particle.
 12. The particle of claim 1,wherein the block copolymer comprises styrene-isobutylene-styrene.
 13. Amethod of making a first particle comprising a block copolymer andhaving at least one pore, the method comprising: generating a dropcomprising the block copolymer and at least one member selected from thegroup consisting of salts, water-soluble polymers, bases, andcombinations thereof; and forming the drop into the first particle. 14.The method of claim 13, wherein forming the drop into the first particlecomprises contacting the drop with a solution comprising water.
 15. Themethod of claim 13, wherein the method comprises generating the dropcomprising the block copolymer and a salt, and forming the drop into thefirst particle comprises dissolving the salt.
 16. The method of claim13, wherein the method comprises generating the drop comprising theblock copolymer and the salt, and the salt comprises at least one saltselected from the group consisting of sodium chloride, calcium chloride,and sodium bicarbonate.
 17. The method of claim 16, wherein the blockcopolymer includes at least one first block having a glass transitiontemperature of at most 37° C. and at least one second block having aglass transition temperature of greater than 37° C.
 18. The method ofclaim 17, wherein the block copolymer comprisesstyrene-isobutylene-styrene.
 19. The method of claim 13, wherein themethod comprises generating the drop comprising the block copolymer andthe water-soluble polymer, and the water-soluble polymer comprises atleast one polymer selected from the group consisting of polyethyleneglycol, polyvinylpyrrolidone, carboxymethylcellulose, andhydroxyethylcellulose.
 20. The method of claim 19, wherein the blockcopolymer includes at least one first block having a glass transitiontemperature of at most 37° C. and at least one second block having aglass transition temperature of greater than 37° C.
 21. The method ofclaim 20, wherein the block copolymer comprises styrene-isobutylenestyrene.
 22. The method of claim 13, wherein forming the drop into thefirst particle comprises contacting the drop with an acid.
 23. Themethod of claim 22, wherein the acid comprises at least one acidselected from the group consisting of citric acid, acetic acid, andhydrochloric acid.
 24. The method of claim 22, wherein contacting thedrop with an acid comprises generating a gas.
 25. The method of claim24, wherein the gas comprises at least one gas selected from the groupconsisting of carbon dioxide, ammonia, and combinations thereof.
 26. Themethod of claim 13, wherein the method comprises generating the dropcomprising the block copolymer and a base, and the base comprises atleast one base selected from the group consisting of sodium bicarbonate,ammonium bicarbonate, and potassium bicarbonate.
 27. The method of claim26, wherein the block copolymer includes at least one first block havinga glass transition temperature of at most 37° C. and at least one secondblock having a glass transition temperature of greater than 37° C. 28.The method of claim 27, wherein forming the drop into the first particlecomprises contacting the drop with an acid.
 29. A method of making aparticle comprising a block copolymer and having at least one pore, themethod comprising: forming a drop comprising the block copolymer and asolvent; and removing some or all of the solvent from the drop to formthe particle.
 30. The method of claim 29, wherein removing some or allof the solvent from the drop comprises exposing the drop to anatmosphere having a pressure of less than 30 inches Hg.
 31. The methodof claim 30, wherein removing some or all of the solvent from the dropcomprises exposing the drop to a temperature of at least about 40° C.32. The method of claim 31, wherein the block copolymer includes atleast one first block having a glass transition temperature of at most37° C. and at least one second block having a glass transitiontemperature of greater than 37° C.
 33. The method of claim 32, whereinthe block copolymer comprises styrene-isobutylene-styrene.
 34. Themethod of claim 29, wherein removing some or all of the solvent from thedrop comprises exposing the drop to a temperature of at least about 40°C.